NCERT Exemplar Class 8 Maths Chapter 8 Exponents and Powers

In this chapter, we provide NCERT Exemplar Problems Solutions for Class 8 Maths Chapter 8 Exponents and Powers for English medium students, Which will very helpful for every student in their exams. Students can download the latest NCERT Exemplar Problems Solutions for Class 8 Maths Chapter 8 Exponents and Powerss pdf, free NCERT Exemplar Problems Solutions for Class 8 Maths Chapter 8 Exponents and Powers book pdf download. Now you will get step by step solution to each question.

TextbookNCERT
ClassClass 8
SubjectMaths
ChapterChapter 8
Chapter NameExponents and Powers
CategoryNCERT Exemplar

NCERT Exemplar Class 8 Maths Chapter 8 Exponents and Powers

Multiple Choice Questions
Question. 1 In 2n, n is known as
(a) base (b) constant
(c) exponent (d) variable
Solution.
(c) We know that an is called the nth power of a; and is also read as a raised to the power n.
The rational number a is called the base and n is called the exponent (power or index). In the same way in 2n,n is known as exponent.

Question. 2 For a fixed base, if the exponent decreases by 1, the number becomes
(a) one-tenth of the previous number
(b) ten times of the previous number
(c) hundredth of the previous number
(d) hundred times of the previous number
Solution.
(a) For a fixed base, if the exponent decreases by 1, the number becomes one-tenth of the previous number.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-1

Question. 3
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-3

Question. 4 The value of 1/4-2 is
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-4

Question. 5 The value of 35   ÷ 3-6  is
(a) 35     (b) 3-6        (c) 311       (d) 3-11
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-5

Question. 6
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-6
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-7

Question. 7
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-8
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-9

Question. 8 The multiplicative inverse of 10-100 is
(a) 10      (b) 100     (c) 10100    (d)10-100 
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-10

Question.9 The value of (-2)2 x 3-1 is
(a) 32      (b) 64       (c) -32    (d) -64
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-11

Question.10
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-12
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-13

Question. 11
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-14
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-15

Question. 12 If x be any non-zero integer and w, n be negative integers, then xm  x xnis equal to
(a) xm     (b)x(m+n)(c) xn(d) x(m-n)
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-16

Question. 13 If y be any non-zero integer, then y0 is equal to
(a) 1                (b) 0                (c) – 1               (d) not defined
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-17

Question.14 If x be any non-zero integer, then X-1 is equal to
(a) x           (b) 1/x           (c) – x         (d) -1/x
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-19

Question. 15
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-20
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-21

Question. 16
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-22
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-23

Question. 17
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-24
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-25

Question. 18
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-26
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-27

Question. 19
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-29

Question. 20
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-31

Question. 21
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-33

Question. 22
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-34
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-35

Question. 23
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-36
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-37

Question.24 The standard form for 0.000064 is
(a) 64 x 104   (b) 64 x 10-4  (c) 6.4 x 105 (d) 6.4 x 10-5
Solution.
(d) Given, 0.000064 = 0. 64 x 10-4 =6.4 x 10-5
Hence, standard form of 0.000064 is 6.4 x 10-5.

Question. 25 The standard form for 234000000 is
(a) 2.34 x 108   (b) 0.234 x 109   
(c) 2.34 x 10-8   (d) 0.234 x 10– 9   
Solution.
(a) Given, 234000000 = 234 x 106 = 2.34 x 10+6  = 2.34 x 108
Hence, standard form of 234000000 is 2.34 x 108.

Question.26 The usual form for 2.03 x 10-5 is    
(a) 0.203 (b) 0.00203 (c) 203000 (d) 0.0000203
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-38

Question. 27
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-39
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-40

Question. 28
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-41
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-42

Question. 29
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-43
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-44

Question. 30
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-45
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-46

Question. 31
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-47
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-48

Question. 32
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-49
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-50

Question. 33
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-51
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-52

Fill in the Blanks
In questions 34 to 65, fill in the blanks to make the statements true.

Question. 34 The multiplicative inverse of 1010 is_________
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-53

Question.35 ax a-10= _________
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-54

Question.36 50 = _________
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-264

Question.37 5x 5-5= _________
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-265

Question.38
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-56
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-57

Question. 39 The expression for 8-2 as a power with the base 2 is_________
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-58

Question. 40 Very small numbers can be expressed in standard form by using_________
exponents
Solution.
Very small numbers can be expressed in standard form by using negative exponents, i.e. 0.000023 = 2.3 x 10-3

Question. 41 Very large numbers can be expressed in standard form by using
exponents.
Solution.
Very large numbers can be expressed in standard form by using positive exponents,
i.e. 23000 = 23 x 103 =2.3 x 10x 101 =2.3 x 104

Question. 42 By multiplying (10)by (10)-10, we get
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-59

Question.43
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-60
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-61

Question.44
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-62
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-63

Question.45
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-64
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-65

Question.46
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-66
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-67

Question.47
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-68
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-69

Question.48
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-70
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-71

Question.49
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-72
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-73

Question.50
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-74
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-75

Question.51
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-76
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-77

Question.52
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-266
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-267

Question.53 The value of 3 x 10-7   is equal to_______
Solution
Given, 3 x 10-7   = 3.0 x 10-7   
Now, placing decimal seven place towards left of original position, we get 0.0000003. Hence, the value of 3 x 10-7 is equal to 0.0000003.

Question.54 To add the numbers given in standard form, we first convert them into number with_______exponents.
Solution.
To add the numbers given in standard form, we first convert them into numbers with equal exponents.
e.g. 2.46 x 106   + 24.6 x 105 = 2.46 x 105 + 2.46 x 106 = 4.92 x 106

Question.55 The standard form for 32500000000 is_______.
Solution.
For standard form, 32500000000 = 3250 x 102 x 102 x 103
= 3250 x 107 = 3.250 x 1010 or 3.25 x 1010
Hence, the standard form for 32500000000 is 3.25 x 1010.

Question. 56 The standard form for 0.000000008 is_______.
Solution.
For standard form, 0.000000008 = 0.8 x 10-8= 8 x  10-9 =8.0 x 10-9
Hence, the standard form for 0.000000008 is 8.0 x 10-9

Question.57 The usual form for 2.3 x 10-10 is_______.
Solution. For usual form, 2.3 x 10-10 = 0.23 x 10-11
= 0.00000000023
Hence, the usual form for 2.3 x 10-10 is 0.00000000023.

Question. 58 On dividing 85 by_______. we get 8.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-78

Question. 59
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-79
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-80

Question. 60
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-81
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-82

ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-83

Question.61
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-84
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-85

Question.62
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-86
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-87

Question.63
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-88
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-89

Question.64
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-90
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-91

Question.65
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-92
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-93

True / False
In questions 66 to 90, state whether the given statements are True or False.

Question.66
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-94
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-95

Question.67
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-96
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-97

Question.68
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-98
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-99

Question.69 24.58 = 2 x 10 + 4 x 1+5 x 10 + 8 x 100
Solution. False
R H S = 2 x 10+ 4 x 1+ 5 x 10+ 8 x 100=20+ 4 + 50+ 800=874 L H S ≠ R H S

Question.70 329.25 = 3 x 102+ 2 x 101 + 9 x 100 + 2 x 10-1 + 5 x 10-2
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-100

Question.71
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-101
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-102

Question.72
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-103
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-104

Question.73
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-105
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-106

Question. 74 50 = 5
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-107

Question. 75 (-2)0 = 2
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-108

Question.76
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-109
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-110

Question. 77 (-6)° = – 1
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-111

Question. 78
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-112
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-113

Question. 79
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-114
Solution.

Question. 80

Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-117

Question. 81
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-118
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-119

Question. 82
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-120
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-121

Question. 83
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-122
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-123

Question. 84

Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-125

Question.85 The standard form for 0.000037 is 3.7 x 10-5
Solution. True
For standard form, 0.000037 = 0.37 x 10-4= 3.7 x 10-5

Question. 86 The standard form for 203000 is 2.03 x 105.
Solution. True
For standard form, 203000 = 203 x 10 x 10 x 10 = 203 x 103
= 2.03 x 102 x 103= 2.03 x 105

Question. 87 The usual form for 2 x 10-2 is not equal to 0.02.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-126

Question. 88 The value of 5-2 is equal to 25.
Solution. False
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-127

Question. 89 Large numbers can be expressed in the standard form by using positive exponents.
Solution.True
e.g. 2360000 = 236 x 10 x 10 x 10 x 10= 236 x 104
‘ = 2.36 x 104 x 102=2.36 x 106

Question. 90
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-128
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-129

Question. 91 Solve the following,
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-130
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-131

Question. 92 Express 3-5 x 3-4 as a power of 3 with positive exponent.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-132

Question. 93 Express 16-2 as a power with the base 2.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-133

Question. 94
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-134
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-135

Question. 95
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-136
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-137

Question. 96 Express as a power of a rational number with negative exponent.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-138
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-139

Question. 97 Find the product of the cube of (-2) and the square of (+4).
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-140

Question.98 Simplify
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-141
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-142
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-143

Question. 99 Find the value of x, so that
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-144
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-145
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-146
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-147

Question. 100 Divide 293 by 1000000 and express the result in standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-148

Question. 101
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-149
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-150

Q. 102 By what number should we multiply (-29)°, so that the product becomes (+29)°.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-151

Question. 103 By what number should (-15)-1 be divided so that quotient may be equal to (-15)-1 ?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-152

Question.104 Find the multiplicative inverse of (-7)2÷ (90)-1
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-153

Question.105
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-154
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-155

Question.106 Write 390000000 in the standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-156

Question. 107 Write 0.000005678 in the standard form.
Solution.
For standard form, 0.000005678 = 0.5678 x 10-5= 5.678 x 10-5 x 10-1= 5.678 x 10-6 Hence, 5.678 x 10-6 is the standard form of 0.000005678.

Question.108 Express the product of 3.2 x 106 and 4.1 x 101 in the standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-157

Question.109
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-158
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-159

Question. 110 Some migratory birds travel as much as 15000 km to escape the extreme climatic conditions at home. Write the distance in metres using scientific notation.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-160

Question. 111 Pluto is 5913000000 m from the Sun. Express this in the standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-161

Question. 112 Special balances can weigh something as 0.00000001 gram. Express this number in the standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-162

Question. 113 A sugar factory has annual sales of 3 billion 720 million kilograms of sugar. Express this number in the standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-163

Question. 114 The number of red blood cells per cubic millimetre of blood is approximately mm3)
Solution. The average body contain 5 L of blood.
Also, the number of red blood cells per cubic millimetre of blood is approximately 5.5 million.
Blood contained by body = 5 L = 5 x 100000 mm3
Red blood cells = 5 x 100000 mm3
Blood = 5.5 x 1000000 x 5 x 100000= 55 x 5 x 105 + 5
= 275 x 1010 = 2.75 x 1010 x 102 = 2.75 x 1012

Question. 115 Express each of the following in standard form:
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-164
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-165
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-166
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-167

Question.116
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-168
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-169
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-170

Question.117
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-171
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-172

In questions 118 and 119, find the value of n.
Question.118
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-173
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-174

Question.119
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-175
Solution.
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Question.120
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Solution.
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Question.121
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Solution.
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Question.122
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Solution.
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Question.123 A new born bear weights 4 kg. How many kilograms might a five year old bear weight if its weight increases by the power of 2 in 5 yr?
Solution.
Weight of new born bear = 4 kg
Weight increases by the power of 2 in 5 yr.
Weight of bear in 5 yr = (4)2 = 16 kg

Question.124 The cell of a bacteria doubles in every 30 min. A scientist begins with a single cell. How many cells will be thereafter (a) 12 h (b) 24 h ?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-183

Question.125 Planet A is at a distance of 9.35 x 106 km from Earth and planet B is 6.27 x 107 km from Earth. Which planet is nearer to Earth?
Solution.
Distance between planet A and Earth = 9.35 x 10km Distance between planet B and Earth = 6.27 x 107 km
For finding difference between above two distances, we have to change both in same exponent of 10, i.e. 9.35 x.106 = 0.935 x 107, clearly 6.27 x 107 is greater.
So, planet A is nearer to Earth.

Question.126 The cells of a bacteria double itself every hour. How many cells will be there after 8 h, if initially we start with 1 cell. Express the answer in powers.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-184

Question. 127 An insect is on the 0 point of a number line, hopping towards 1. She covers half the distance from her current location to 1 with each hop.
So, she will be at 1/2 after one hop, 3/4 after two hops and so on.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-185
(a) Make a table showing the insect’s Location for the first 10 hops.
(b) Where will the insect be after n hops?
(c) Will the insect ever get to 1? Explain.
Solution.
(a) On the basis of given information in the question, we can arrange the following table which shows the insect’s location for the first 10 hops.
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ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-187

Question. 128 Predicting the ones digit, copy and complete this table and answer the questions that follow.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-188

Solution.
(a) On the basis of given pattern in 1x and 2x , we can make more patterns for 3x 4x , 5x ,6x , 7x , 8x , 9x , 10x .
Thus, we have following table which shows all details about the patterns.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-189

Question. 129 Astronomy The table shows the mass of the planets, the Sun and the Moon in our solar system.
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-191

Question. 130 Investigating Solar System The table shows the average distance from each planet in our solar system to the Sun.
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-193

Question. 131 This table shows the mass of one atom for five chemical elements.
Use it to answer the question given.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-194
(a) Which is the heaviest element?
(b) Which element is lighter, Silver or Titanium?
(c) List all the five elements in order from lightest to heaviest.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-195

Question. 132 The planet Uranus is approximately 2,896,819,200,000 metres away from the Sun. What is this distance in standard form?
Solution.
Distance between the planet Uranus and the Sun is 2896819200000 m.
Standard form of 2896819200000 = 28968192 x 10 x 10 x 10 x 10 x 10
= 28968192 x 105 = 2.8968192 x 1012 m

Question. 133 An inch is approximately equal to 0.02543 metres. Write this distance in standard form.
Solution. Standard form of 0.02543 m = 0.2543 x 10-1 m = 2.543 x 10-2 m Hence,’ standard form of 0.025434s 2.543 x 10-2 m.

Question.134 The volume of the Earth is approximately 7.67 x 10-7 times the volume
of the Sun. Express this figure in usual form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-196

Question.135 An electron’s mass is approximately 9.1093826 x 10-31 kilograms. What is its mass in grams?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-197

Question. 136 At the end of the 20th century, the world population was approximately 6.1 x 109 people. Express this population in usual form. How would you say this number in words?
Solution.
Given, at the end of the 20th century, the world population was 6,1 x 109 (approx). People population in usual form = 6.1 x 109 = 6100000000 Hence, population in usual form was six thousand one hundred million.

Question.137 While studying her family’s history, Shikha discovers records of ancestors 12 generations back. She wonders how many ancestors she had in the past 12 generations. She starts to make a diagram to help her figure this out. The diagram soon becomes very complex
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-198
Solution.
(a) On the basis of given diagram, we can make a table that shows the number of ancestors in each of the 12 generations.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-199

Question. 138 About 230 billion litres of water flows through a river each day, how many litres of water flows through that river in a week? How many litres of water flows through the river in an year? Write your answer in standard notation.
Solution.
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Question. 139 A half-life is the amount of time that it takes for a radioactive substance to decay one-half of its original quantity.
Suppose radioactive decay causes 300 grams of a substance to decrease 300 x 2-3 grams after 3 half-lives. Evaluate 300 x 2-3 to determine how many grams of the substance is left.
Explain why the expression 300 x 2-n can be used to find the amount of the substance that remains after n half-lives.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-201

Question. 140 Consider a quantity of a radioactive substance. The fraction of this quantity that remains after t half-lives can be found by using the expression 3-t.
(a) What fraction of the substance remains after 7 half-lives?
(b) After how many half-lives will the fraction be 1/243 of the original?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-202

Question. 141 One fermi is equal to 10-15 metre. The radius of a proton is 1.3 fermi. Write the radius of a proton (in metres) in standard form.
Solution. The radius of a proton is 1.3 fermi.
One fermi is equal to 10-15 m.
So, the radius of the proton is 1.3 x 10-15 m.
Hence, standard form of radius of the proton is 1.3 x  10-15 m.

Question. 142 The paper clip below has the indicated length. What is the length in Standard form.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-203
Solution.

Length of the paper clip = 0.05 m
In standard form, 0.05 m = 0.5 x 10-1 = 5.0 x 10-2 m
Hence, the length of the paper clip in standard form is 5.0 x 10-2 m

Question.143 Use the properties of exponents to verify that each statement is true.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-204
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-205

Question. 144 Fill in the blanks.
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Solution.
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Question. 145 There are 86400 sec in a day. How many days long is a second? Express your answer in scientific notation.
Solution. Total seconds in a day = 86400
So, a second is long as 1/86400 = 0.000011574
Scientific notation of 0.000011574= 1.1574 x 10-5days

Question. 146 The given table shows the crop production of a state in the year 2008 and 2009. Observe the table given below and answer the given questions.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-208
(a) For which crop(s) did the production decrease?
(b) Write the production of all the crops in 2009 in their standard form.
(c) Assuming the same decrease in rice production each year as in 2009, how many acres will be harvested in 2015? Write in standard form.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-209

Question. 147 Stretching Machine
Suppose you have a stretching machine which could stretch almost anything, e.g. If you put a 5 m stick into a (x 4) stretching machine (as shown below), you get a 20 m stick.
Now, if you put 10 cm carrot into a (x 4) machine, how long will it be when it comes out?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-210
Solution.
According to the question, if we put a 5 m stick into a (x 4) stretching machine, then machine produces 20 m stick.
Similarly, if we put 10 cm carrot into a (x 4) stretching machine, then machine produce 10 x 4= 40 cm stick.

Question. 148 Two machines can be hooked together. When something is sent through this hook up, the output from the first machine becomes the input for the second.
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Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-212

Question. 149 Repeater Machine
Similarly, repeater machine is a hypothetical machine which automatically enlarges items several times, e.g. Sending a piece of wire through a (x 24) machine is the same as putting it through a (x 2) machine four times. ‘
So, if you send a 3 cm piece of wire thorugh a (x 2)4 machine, its length becomes 3 x 2 x 2 x 2 x 2 = 48 cm. It can also be written that a base (2) machine is being applied 4 times.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-213
What will be the new length of a 4 cm strip inserted in the machine?
Solution.
According to the question, if we put a 3 cm piece of wire through a (x 24) machine, its length becomes 3 x 2 x 2 x 2 x 2 = 48 cm.
Similarly, 4 cm long strip becomes 4 x 2 x 2 x 2 x 2 = 64 cm.

Question. 150 For the following repeater machines, how many times the base machine is applied and how much the total stretch is?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-214
Solution.
In machine (a), (x 100 2) = 10000stretch. Since, it is two times the base machine.
In machine (b), (x 7 5) = 16807 stretch.
Since, it is fair times the base machine.
In machine (c), (x 57) = 78125stretch.
Since, it is 7 times the base machine.

Question. 151 Find three repeater machines that will do the same work as a (x 64) machine. Draw them, or describe them using exponents.’
Solution.
We know that, the possible factors of 64 are 2, 4, 8. :
If 26 =64, 43 =64 and 82 =64
Hence, three repeater machines that would work as a (x 64) will be (x 26 ), (x 43) and (x 82). The diagram of (x 26), (x 43)and (x 82)is given below.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-215

Question. 152 What will the following machine do to a 2 cm long piece of chalk?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-216
Solution.
The machine produce x 1100=1
So, if we insert 2 cm long piece of chalk in that machine, the piece of chalk remains same.

Question. 153 In a repeater machine with 0 as an exponent, the base machine is applied 0 times.
(a) What do these machines do to a piece of chalk?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-217
(b) What do you think the value of 6° is?
You have seen that a hookup of repeater machines with the same base can be replaced by a single repeater machine. Similarly, when you multiply exponential expressions with the same base, you can replace them with a single expression.
Asif Raza thought about how he could rewrite the expression 220 x 25.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-218
Asif Raza’s idea is one of the product laws of exponents, which can be expressed like this
Multiplying Expressions with the Same Base ab x ac = ab+ c
Actually, this law can be used with more than two expressions. As long as the bases are the same, to find the product you can add the exponents and use the same base.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-219

Question. 154 Shrinking Machine In a shrinking machine, a piece of stick is compressed to reduce its length. If 9 cm long sandwich is put into the shrinking machine below, how long will it be when it emerges?

Solution.
According to the question, in a shrinking machine, a piece of stick is compressed to reduce its length. If 9 cm long sandwich is put into the shrinking machine, then the length
of sandwich will be 9 x 1/ 3-1= 9 x 3 = 27 cm.

Question. 155 What happens when 1 cm worms are sent through these hook-ups?

Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-222

Question. 156 Sanchay put a 1 cm stick of gum through a (1 x 3-2) machine. How
long was the stick when it came out?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-223

Question. 157 Ajay had a 1 cm piece of gum. He put it through repeater machine
given below and it came out 1/100000 cm long. What is the missing
value?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-224
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-225

Question. 158 Find a single machine that will do the same job as the given hook-up.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-226
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-227
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-228

Question. 159 Find a single repeater machine that will do the same work as each hook-up.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-229
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-230
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-231

Question. 160 For each hook-up, determine whether there is a single repeater
machine that will do the same work. If so, describe or draw it.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-232
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-233
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-234

Question. 161 Shikha has an order from a golf course designer to put palm trees through a (x 23) machine and then through a (x 33) machine. She thinks that she can do the job with a single repeater machine. What single repeater machine she should use?
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-235
Solution.
Sol. The work done by hook-up machine is equal to 2 x 2 x 2 x 3 x 3 x 3 = 216 = 63 So, she should use (x 63) single machine for the purpose.

Question. 162 Neha needs to stretch some sticks to 252 times of their original lengths, but her (x 25) machine is broken. Find a hook-up of two repeater machines that will do the same work as a (x 252) machine. To get started, think about the hook-up you could use to replace the (x 25) machine.

Solution.
Work done by single machine (x 252) = 25 x 25 = 625 or 5 x 5 x 5 x 5 or 52 x 52
Hence, (x 52) and (x 52) hook-up machine can replace the (x 25) machine.

Question.163 Supply the missing information for each diagram.

solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-238

Question. 164 If possible, find a hook-up of prime base number machine that will do the same work as the given stretching machine. Do not use (x 1) machines.

solution.
(a) Single machine work = 100
Hook-up machine of prime base number that do the same work down by x 100
= 22 x 52
=4×25
= 100
(b) x 99 = 32 x 111 hook-up machine.
(c) x 37 machine cannot do the same work.
(d) x 1111 = 101 x 11 hook-up machine.

Question. 165 Find two repeater machines that will do the same work as a (x 81) machine.
Solution. Two repeater machines that do the same work as (x 81) are (x 34) and (x 92).
Since, factor of 81 are.3 and 9.

Question. 166
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-240
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-241

Question. 167 Find three machines that can be replaced with hook-up of (x 5) machines.
Solution.
Since, 52 = 25, 53 = 125, 54 = 625
Hence, (x 52), (x 53)and (x 54) machine can replace (x 5) hook-up machine.

Question. 168 The left column of the chart lists is the length of input pieces of ribbon. Stretching machines are listed across the top.
The other entries are the outputs for sending the input ribbon from that row through the machine from that column. Copy and complete the chart.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-242
Solution.
In the given table, the left column of chart list is the length of input piece of ribbon. Thus, the outputs for sending the input ribbon are given in the following table.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-243

Question. 169 The left column of the chart lists is the length of input chains of gold. Repeater machines are listed across the top. The other entries are the outputs you get when you send the input chain from that row through the repeater machine from that column. Copy and complete the chart.

Solution.
In the given table, the left column of the chart lists is the length of input chains of gold. Thus, the output we get when we send the input chain from the row through the repeater machine are detailed in the following table.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-245

Question.170 Long back in ancient times, a farmer saved the life of a king’s daughter. The king decided to reward the farmer with whatever he wished. The farmer, who was a chess champion, made an unusal request
“I would like you to place 1 rupee on the first square of my chessboard. 2 rupees on the second square, 4 on the third square, 8 on the fourth square and so on, until you have covered all 64 squares. Each square should have twice as many rupees as the previous square.” The king thought this to be too less and asked the farmer to think of some , better reward, but the farmer didn’t agree.
How much money has the farmer earned?
[Hint The following table may help you. What is the first square on which the king will place atleast Rs. 10 lakh?]
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-246
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-247

Question. 171 The diameter of the Sun is 1.4 x 109 m and the diameter of the Earth is 1.2756 x 10m. Compare their diameters by division.
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-248

Question. 172 Mass of Mars is 6.42 x 1029 kg and mass of the Sun is 1.99 x 1030 kg. What is the total mass?
Solution.
Mass of Mars = 6.42 x 1029  kg
Mass of the Sun = 1.99 x 1030 kg
Total mass of Mars and Sun together = 6.42 x 1029  + 1.99 x 1030
= 6.42 x 1029  + 19.9 x 1029  = 26.32 x 1029  kg

Question. 173 The distance between the Sun and the Earth is 1.496 x 108 km and : distance between the Earth and the Moon is 3.84 x 108 m. During
solar eclipse, the Moon comes in between the Earth and the Sun. What is the distance between the Moon and the Sun at that particular time?
Solution.
The distance between the Sun and the Earth is 1.496 x 10s km
= 1.496 x 108 x 103 m = 1496 x 108 m
The distance between the Earth and the Moon is 3.84 x108 m.
The distance between the Moon and the Sun at particular time (solar eclipse) = (1496 x 108-3.84 x 108)m = 1492.   16 x 108 m

Question. 174 A particular star is at a distance of about 8.1 x 1013 km from the Earth. Assuring that light travels at 3 x 108 m per second, find how long does light takes from that star to reach the Earth?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-249

Question. 175 By what number should (-5)-1 be divided so that the quotient may be equal to (-5)-1?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-250

Question. 176 By what number should (-8)-3 .be multiplied so that the product may be equal to (-6)-3?
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-251

Question. 177 Find x.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-252
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-253
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-254
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-255

Question. 178 If a = – 1, b = 2,-then find the value of the following,
(i) ab+ ba   (ii) ab – ba
(iii) ab x b(iv) ab ÷ ba
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-256

Question.179 Express each of the following in exponential form.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-257
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-258
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-259

Question. 180 Simplify
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-260
Solution.
ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-261
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ncert-exemplar-problems-class-8-mathematics-exponents-and-powers-263

All Chapter NCERT Exemplar Problems Solutions For Class 8 maths

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All Subject NCERT Exemplar Problems Solutions For Class 8

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