NCERT Solutions For Class 8 Maths Chapter 10 Exponents And Powers

Exponents And Powers

Exponents And Powers Introduction

If a is any non-zero integer and n is a positive integer, then

x a (n times) is written as a”,

i.e., a” is the continued product of a multiplied by itself n times.

Here, ‘o’ is called the base, and V is called the ‘exponent’ or ‘index’.

The number a” is read as a raised to the power of or simply as ‘nth power of o’.

The notation a” is called the exponential or power notation.

We can write large numbers more conveniently using exponents.

For example :

10000 = 104; 243 = 35; 128 = 27, etc.

Now, we shall learn about negative exponents

Read and Learn More NCERT Solutions For Class 8 Maths

Powers With Negative Exponents

If a is any non-zero integer and m is a positive integer, then

⇒ \(a^{-m}=\frac{1}{a^m}\)

Note: a m is called the multiplicative inverse of am as a-m x am = 1

Am and a ~m are multiplicative inverses of each other.

Note 2: \(a^m=\frac{1}{a^{-m}}\)

Question: What is 10 ~10 equal to?

Solution: \(10^{-10}=\frac{1}{10^{10}}\)

Question 1. Find the multiplicative inverse of the following:

  1. 2-4
  2. 10-5
  3. 7-2
  4. 5-3
  5. 10-100

Solution:

The multiplicative inverse is \(2^{-4}=\left(\frac{1}{2^{-4}}\right) \text { is } 2^4\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

The multiplicative inverse of \(10^{-5}=\left(\frac{1}{10^{-5}}\right) \text { is } 10^5\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

The multiplicative inverse of \(7^{-2}=\left(\frac{1}{7^{-2}}\right) \text { is } 7^2\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

The multiplicative inverse \(5^{-3}=\left(\frac{1}{5^{-3}}\right) \text { is } 5^3\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

The multiplicative inverse\(10^{-100}=\left(\frac{1}{10^{-100}}\right) \text { is } 10^{100}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

Question 2. Expand the following numbers using exponents :

  1. 1025.63
  2. 1256.249

Solution:

1025.63

1 x 1000 + 0 x 100 + 2 x 10 + 5 x 1 + 6 x\(\frac{1}{10}+3 \times \frac{1}{100}\)

= 1 x 103 + 0 x 102 + 2 x 101 + 5 x 10° + 6 x 10-1 + 3 x 10-2

1256.249

= 1 x 1000 + 2 x 100 + 5 x 10

+ 6x 1+ 2 x \( \frac{1}{10}+4 \times \frac{1}{100}+9 \times \frac{1}{1000}\)

= 1 X 103 + 2 X 102 + 5 X 101 + 6 x 10° + 2 x 10-1 + 4 x 10-2 + 9 x lO-3

Laws Of Exponents

If a, b are non-zero integers and m, n are any integers, then

  1. am x an = am+ n
  2. \(\frac{a^m}{a^n}=a^{m-n}\)
  3. (am)n = amn
  4. am x bm = (ab)m
  5. \(\frac{a^m}{b^m}=\left(\frac{a}{b}\right)^m\)
  6. a° = 1
  7. \(\left(\frac{a^{-m}}{b^{-n}}\right)=\frac{b^n}{a^m}\)
  8. \(\left(\frac{a}{b}\right)^{-m}=\left(\frac{b}{a}\right)^m\)

Remember

an” = 1 = n = 0

1n = 1 where n is any integer.

(- 1)n = 1 where n is any even integer.

(-1)n =-1 where n is any odd integer.

Q. Simplify and write in exponential form:

(-2)-3X (-2)-4

p3 x p -I0

32 x 3-5 x 36

Solution:

(-2)~3 x (-2)-4 = (- 2)(“3) + (-4>

am x an = am +n

= (-2)-7 = {(-1) x 2} -7

⇒ \(\frac{1}{\{(-1) \times 2\}^7}= \frac{1}{(-1)^7 \times(2)^7}\)

(ab)m = am bm

⇒ \(\frac{1}{(-1) \times 2^7}=-\frac{1}{2^7}\)

⇒ \(\mid(-1)^{\text {odd integer }}=-1\)

⇒ \(p^3 \times p^{-10}=p^{3+(-10)}=p^{-7}=\frac{1}{p^7}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

32 x 3-5 x 36 = 32 + (-5) + 6 = 33

Exponents And Powers Exercise 10.1

Question 1. Evaluate:

  1. 3-2
  2. (-4)-2
  3. \(\left(\frac{1}{2}\right)^{-5}\)

Solution:

⇒ \(3^{-2}=\frac{1}{3^2}=\frac{1}{9}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \((-4)^{-2}=\frac{1}{(-4)^2}=\frac{1}{16}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\left(\frac{1}{2}\right)^{-5}=\left(\frac{2}{1}\right)^5\)

⇒ \( a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{2^5}{1^5}\)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \(\frac{32}{1}=32\)

1n = 1 where n is an integer

Question 2. Simplify and express the result in power notation with a positive exponent

  1. \((-4)^5 \div(-4)^8\)
  2. \(\left(\frac{1}{2^3}\right)^2\)
  3. \((-3)^4 \times\left(\frac{5}{3}\right)^4\)
  4. (3-7 – 3-10) x 3-5
  5. 2-3 x (-7) -3

Solution:

1. (-4)6 ÷ (-4)8

⇒ \(\frac{(-4)^5}{(-4)^8}\)

⇒ \((-4)^{5-8}\)

⇒ \((-4)^{-3}\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(=\frac{1}{(-4)^3}  a^{-m}=\frac{1}{a^m}\)

which is the required form.

2. \(\left(\frac{1}{2^3}\right)^2 =\frac{1^2}{\left(2^3\right)^2}\)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \(\frac{1}{2^{3 \times 2}} \)

⇒ \( \mid\left(a^m\right)^n=a^m\)

⇒ \(\frac{1}{2^6}\)

which is the required form

3. \((-3)^4 \times\left(\frac{5}{3}\right)^4=\{(-1) \times 3\}^4 \times \frac{5^4}{3^4} \)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \((-1)^4(3)^4 \times \frac{5^4}{3^4}\)

I (ab)m = am bm

= (- 1)4 x 54

= 1 x 54

(-1) even integer = 1

= 54

which is the required form.

4. (3-7 / 3-10) x 3-5

⇒ \(=\frac{3^{-7}}{3^{-10}} \times \frac{1}{3^5}\)

⇒ \( a^{-m}=\frac{1}{a^m}\)

⇒ \(3^{-7-(-10)} \times \frac{1}{3^5}\)

⇒ \(\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(3^3 \times \frac{1}{3^5} \)

⇒ \(\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(3^{3-5} \)

⇒ \(3^{-2} \)

⇒ \(a^{-m}=\frac{1}{a^m}\)

which is the required form.

5. \(2^{-3} \times(-7)^{-3}\)

⇒ \(\frac{1}{2^3} \times \frac{1}{(-7)^3}\)

⇒ \(\frac{1}{[2 \times(-7)]^3}=\frac{1}{a^m}\)

(ab)m = amb

⇒ \(\frac{1}{(-14)^3}\)

which is the required form.

Question 3. Find the value of:

(3° + 4 -1) x 22

(2-1 x 4-1)/2 -2

⇒ \(\left(\frac{1}{2}\right)^{-2}+\left(\frac{1}{3}\right)^{-2}+\left(\frac{1}{4}\right)^{-2}\)

⇒ \(\left(3^{-1}+4^{-1}+5^{-1}\right)^0\)

⇒ \(\left\{\left(\frac{-2}{3}\right)^{-2}\right\}^2.\)

Solution:

1. (3° + 4-1) x 22

⇒ \(\left(1+\frac{1}{4}\right) \times 4\)

⇒ \(a^{-m}=\frac{1}{a^m}, \quad a^0=1\)

⇒ \(\frac{5}{4} \times 4=5\)

(2-1 x 4-1) + 2″2

= {2 -l x (22)-1} + 2 -2

= {2-1 x 22x(-1>} -f2-2

(am)n = amn

= (2-’X2-2)T2-2 = 2(-1)+(-2) 2-2

am x a” = am+”

= 2-3 4- 2″2

⇒ \(\frac{2^{-3}}{2^{-2}}=2^{-3-(-2)} \)

⇒ \(\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(2^{-1}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{1}{2}\)

3.\(\left(\frac{1}{2}\right)^{-2}+\left(\frac{1}{3}\right)^{-2}+\left(\frac{1}{4}\right)^{-2}\)

⇒ \(\frac{1^{-2}}{2^{-2}}+\frac{1^{-2}}{3^{-2}}+\frac{1^{-2}}{4^{-2}}\)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \(\frac{2^2}{1^2}+\frac{3^2}{1^2}+\frac{4^2}{1^2}\)

⇒ \(\frac{4}{1}+\frac{9}{1}+\frac{16}{1}\)

= 4 + 9 + 16 = 29

4. [3-1 + 4-1 + 5-1]0

⇒ \({\left[\frac{1}{3}+\frac{1}{4}+\frac{1}{5}\right]^0 }\)

⇒ \(\left(\frac{20+15+12}{60}\right)^0\)

⇒ \(\quad \text { | LCM }(3,4,5)=60\)

⇒ \(\left(\frac{47}{60}\right)^0=1\)

\(a^0=1\)

Aliter

(3-1 + 4-1 +5-1)° = 1

a°= 1

5. \(\left\{\left(\frac{-2}{3}\right)^{-2}\right\}^2\)

⇒ \(\left(\frac{-2}{3}\right)^{(-2) \times 2}\)

⇒ \(\mid\left(a^m\right)^n=a^{m n}\)

⇒ \(\left(\frac{-2}{3}\right)^{-4}\)

⇒ \(\left(\frac{3}{-2}\right)^4 \)

⇒ \( \left(\frac{a}{b}\right)^{-m}=\left(\frac{b}{a}\right)^m\)

⇒ \(\frac{3^4}{(-2)^4}=\frac{3^4}{(-1 \times 2)^4}\)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \(\frac{3^4}{(-1)^4(2)^4}\)

⇒ \((a b)^m=a^m b^m\)

⇒ \(\frac{3^4}{1 \times 2^4} \)

⇒ \((-1)^{\text {even integer }}=1\)

⇒ \(\frac{3^4}{2^4}\)

⇒ \(\frac{3 \times 3 \times 3 \times 3}{2 \times 2 \times 2 \times 2}=\frac{81}{16}\)

Question 4. Evaluate:

  1.  \(\frac{8^{-1} \times 5^3}{2^{-4}}\)
  2.  \(\left(5^{-1} \times 2^{-I}\right) \times 6^{-1}\)

Solution:

1. \(\frac{8^{-1} \times 5^3}{2^{-4}}\)

⇒ \(\frac{2^4 \times 5^3}{8^1}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{16 \times 125}{8}=250\)

2. \(\left(5^{-1} \times 2^{-1}\right) \times 6^{-1}=\left(\frac{1}{5} \times \frac{1}{2}\right) \times \frac{1}{6}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{1}{10} \times \frac{1}{6}=\frac{1}{60}\)

Question 5. Find the value of m for which 5m + 5-3 = 55
Solution:

5m + 5-3 = 55

⇒ \(\frac{5^m}{5^{-3}} =5^5\)

⇒ \(5^{m-(-3)} =5^5\)

⇒ \(\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(5^{m+3} =5^5\)

bases are equal exponents are equal

m + 3 = 5

m = 5-3

m = 2

Question 6. Evaluate:

  1. \(\left\{\left(\frac{1}{3}\right)^{-1}-\left(\frac{1}{4}\right)^{-1}\right\}^{-1}\)
  2. \(\left(\frac{5}{8}\right)^{-7} \times\left(\frac{8}{5}\right)^{-4}.\)

Solution:

⇒ \(\left\{\left(\frac{1}{3}\right)^{-1}-\left(\frac{1}{4}\right)^{-1}\right\}^{-1}\)

⇒ \(\left(\frac{1^{-1}}{3^{-1}}-\frac{1^{-1}}{4^{-1}}\right)^{-1}\)

⇒ \(\left(\frac{a}{b}\right)^m=\frac{a^m}{b^m}\)

⇒ \(\left\{\frac{\frac{1}{1^1}}{\frac{1}{3^1}}-\frac{\frac{1}{1^1}}{\frac{1}{4^1}}\right\}^{-1}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\left(\frac{3^1}{1^1}-\frac{4^1}{1^1}\right)^{-1}\)

⇒ \(a^1=a\)

⇒ \(\left(\frac{3}{1}-\frac{4}{1}\right)^{-1}\)

⇒ \( (3-4)^{-1}\)

⇒ \((-1)^{-1}=\frac{1}{(-1)^1}\)

⇒ \(| a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{1}{(-1)}\)

\((-1)^{\text {odd integer }}=-1\)= -1

⇒ \(\left(\frac{5}{8}\right)^{-7} \times\left(\frac{8}{5}\right)^{-4}=\frac{5^{-7}}{8^{-7}} \times \frac{8^{-4}}{5^{-4}}\)

⇒ \(\frac{5^{-7}}{5^{-4}} \times \frac{8^{-4}}{8^{-7}}\)

⇒ \(=5^{(-7)-(-4)} \times 8^m=\frac{a^m}{b^m}\)

⇒ \(\frac{a^m}{a^n}=a^{m-n}\)

⇒ \(5^{-7+4} \times 8^{-4}+7 \)

⇒ \(\frac{1}{5^3} \times 8^3=\frac{8^3}{5^3}\)

⇒ \(\frac{8 \times 8 \times 8}{5 \times 5 \times 5}=\frac{512}{125}\)

Question 7. Simplify:

  1. \(\frac{25 \times t^{-4}}{5^{-3} \times 10 \times t^{-8}} \quad(t \neq 0)\)
  2. \(\frac{3^{-5} \times 10^{-5} \times 125}{5^{-7} \times 6^{-5}}\)

Solution:

1. \(\frac{25 \times t^{-4}}{5^{-3} \times 10 \times t^{-8}}\)

⇒ \(\frac{25 \times 5^3}{10} \times \frac{t^8}{t^4}\)

⇒ \(\frac{625}{2} \times \frac{t^8}{t^4}\)

⇒ \(\frac{625 t^4}{2}\)

⇒ \(\frac{3^{-5} \times 10^{-5} \times 125}{5^{-7} \times 6^{-5}}\)

⇒ \(\frac{3^{-5} \times(2 \times 5)^{-5} \times(5 \times 5 \times 5)}{5^{-7} \times(2 \times 3)^{-5}}\)

⇒ \(\frac{3^{-5} \times 2^{-5} \times 5^{-5} \times 5^3}{5^{-7} \times 2^{-5} \times 3^{-5}} \)

⇒ \(\quad(a b)^m=a^m b^m\)

⇒ \(\frac{5^{-5} \times 5^3}{5^{-7}}=\frac{5^{(-5)+3}}{5^{-7}}\)

⇒ \(\mid a^m \times a^n=a^{m+n}\)

⇒ \(\frac{5^{-2}}{5^{-7}}=5^{(-2)-(-7)}\)

⇒ \(5^{-2+7}=5^5\)

Use Of Exponents To Express Small Numbers In Standard Form

A number is said to be in standard form if expressed in the form K x 10″ where 1 < K < 10 and n is an integer. A number written in standard form is said to be expressed in scientific notation.

Tiny numbers can be expressed in standard form using negative exponents.

1. To express a large number, we move the decimal point to the left such that only one digit is left to the left side of the decimal point and multiply the resulting number by 10n where n is the number of places to which the decimal point has been moved to the left.

For example : 270,000,000,000 = 2.7 x 1011

(Decimalpointhas have been moved to the left for11 places)

2. To express a number (< 1), we move the decimal point to the right such that only one digit is left to the left side of the decimal point and multiply the resulting number by 10~’1 where n is the number of places to which the decimal point has been shifted to the right.

For example : 0.000 0009 = 9 x 10-7

(Decimalpointhas have been shifted to the right for 7 places.)

Question 1. Identify huge and very small numbers from the above facts and write them in the following table:

NCERT Solutions For Class 8 Maths Chapter 10 Large And very Small

Solution:

NCERT Solutions For Class 8 Maths Chapter 10 Very Large Numbers

Question 2. Write the following numbers in standard form:

  1. 0.000000564
  2. 0.0000021
  3. 21600000
  4. 15240000

Solution:

1.  0.000000564

= 5.64 x 10-7

Moving decimal 7 places to the right

2.  0.0000021

0.0000021 = 2.1 x 10-6

Moving decimal 6 places to the right

3.  21600000

21600000 = 2.16 x 107

Moving decimal 7 places to the left

4.  15240000

15240000 = 1.524 x 107

Moving decimal 7 places to the left

Question 2. Write all the facts given in the standard form.
Solution:

(1) The distance from the Earth to the Sun is 1.496 x 1011 m

149, 600,000,000 = 1.496 x 1011.

Moving the decimal 11 places to the left

(2) The speed of light is 3 x 108 m/sec.

300, 000, 000 = 3 x108.

Moving decimal 8 places to the left

The thickness of the Class VII Mathematics book is 2 x 101 mm.

20 = 2 x 10 = 2 x 101

The average diameter of a Red Blood Cell is 7 x 10 6 mm.

0.00 0007 = 7 x 10-6

Moving decimal 6 places to the right

The thickness of human hair is in the range of 5 x 10 -3 cm to 1 x I0″2cm

⇒ \(0.005=\frac{5}{1000}=\frac{5}{10^3}=5 \times 10^{-3}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(0.01=\frac{1}{100}=\frac{1}{10^2}=1 \times 10^{-2}\)

The distance of the moon from the Earth is 3.84467 x 108m

384,467,000 = 3.84467 x 108

I Moved the decimal 8 places to the left

(7) The size of a plant cell is 1.275 x 10-5m

0.00001275 = 1.275 x 105

Moving decimal 5 places to the right

The average radius of the Sun is 6.95 x105km

695000 = 695 x 1000 = 695 x 103 = 6.95 x 105

(9) Mass of fuel in a space shuttle

solid rocket booster is 5.036 x 105 kg

503600

= 5036 x 100 = 5036 x 102

= 5.036 x 103 x 102

= 5.036 x 103+2

am x an = am+n

= 5.036 x 105

(10) Thickness of a piece of paper is 1.6 x10-3 cm

0.0016 = 1.6 x 10-3

Moving decimal 3 places to the right

The diameter of wire on a computer chip is 3 x 10-6 m

is 3 x 10-6

0.000003 = 3 x 013

Moving decimal 6 places to the right

(12) The height of Mount Everest is 8.848 x 103  m.

8848 = 8.848 x 1000 = 8.848 x 103

Exponents And Powers Exercise 10.2

Question 1. Express the following numbers in standard form:

  1. 0.0000000000085
  2. 0.00000000000942
  3. 6020000000000000
  4. 0.00000000837
  5. 31860000000.

Solution:

1. 0.0000000000085

0.0000000000085 = 8.5 x 10-12

Moving the decimal 12 places to the right

2. 0.00000000000942

0.00000000000942 = 9.42 x 10-15

Moving the decimal 12 places to the right

3. 6020000000000000

6020000000000000 = 6.02 x 1015

Moving the decimal 15 places to the left

4. 0.00000000837

0.00000000837 = 8.37 x 10-9

Moving decimal 9 places to the right

5. 31860000000

31860000000 = 3.186 x 1010

Moving decimal 10 places to the left

Question 2. Express the following numbers in the usual form:

  1. 3.02 x 10-6
  2. 4.5 x 104
  3. 3 x 10-8
  4. 1.0001 x 109
  5. 5.8 x 1012
  6. 3.61492 x 106

Solution:

⇒ \(3 \times 10^{-8}=\frac{3}{10^8}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(=\frac{3.02}{1000000}\)

⇒ 0.00000302

2. 4.5 x 104 = 4.5 x 10000 = 45000

3.  \(3.02 \times 10^{-6}=\frac{3.02}{10^6}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(\frac{3}{100000000}\)

=0.00000003

4. 1.0001 X 109

= 1.0001 X 1000,000,000

= 1,000,100,000

5. 5.8 X 1012

= 5.8 X 1,000,000,000,000

= 5,800,000,000,000

6. 3.61492 x 106

= 3.61492 x 1,000,000

= 3,614,920

Question 3. Express the number appearing in the following statements in standard form:

  1. 1 micron is equal to \(\frac{1}{1000000} m\)
  2. The charge of an electron is 0. 000, 000,000,000,000,000,1 6 coulomb.
  3. The size of bacteria is 0. 0000005 m
  4. The size of a plant cell is 0. 00001 275 m
  5. The thickness of thick paper is 0.07 mm.

Solution:

1.  \(\frac{1}{1000000} \mathrm{~m}= \frac{1}{10^6}\)

⇒ \(1 \times 10^{-6} \mathrm{~m}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

which is the required standard form.

2.  0.000,000,000,000,000,000,16 coulomb

⇒ \(\frac{16}{100,000,000,000,000,000,000} \text { coulomb }\)

⇒ \(frac{16}{10^{20}} \text { coulomb }\)

⇒ \(\frac{1.6 \times 10}{10^{20}} \text { coulomb }\)

⇒ \(\frac{1.6 \times 10^1}{10^{20}} \text { coulomb } \quad \mid a^1=a\)

⇒ \(1.6 \times 10^{1-20} \text { coulomb } \frac{a^m}{a^n}=a^{m-n}\)

⇒ \(1.6 \times 10^{-19} \text { coulomb }\)

which is the required standard form.

3. 0.0000005 m

⇒ \(\frac{5}{10000000} \mathrm{~m} \)

⇒ \(\frac{5}{10^7} \mathrm{~m}\)

⇒ \(5 \times 10^{-7} \mathrm{~m}\)

which is the required standard form.

4.  \(0.00001275 \mathrm{~m} =\frac{1275}{100,000,000} \mathrm{~m}\)

⇒ \(\frac{1275}{10^8} \mathrm{~m}\)

⇒ \(\frac{1275}{10^3 \times 10^5} \mathrm{~m}\)

| am x a” = am + n

⇒ \(\frac{1275}{10^3} \times 10^{-5} \mathrm{~m}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

⇒ \(1.275 \times 10^{-5} \mathrm{~m}\)

which is the required standard form.

5. \( 0.07 \mathrm{~mm} =\frac{7}{100}\)

⇒ \(\frac{7}{10^2}=7 \times 10^{-2} \mathrm{~mm}\)

⇒ \(a^{-m}=\frac{1}{a^m}\)

which is the required standard form

Question 4. In a stack, there are 5 books each of thickness 20 mm, and 5 paper sheets each of thickness 0. 016mm. What is the total thickness of the stack?
Solution:

Total thickness of books = 5 x 20 mm = 100 mm

Total thickness of paper sheets = 5 x 0.016 mm = 0.080 mm

Total thickness of the stack

= Total thickness of books + Total thickness of paper sheets

= 100 mm + 0.080 mm

= (100 + 0.080) mm

= 100.080 mm

= 1.0008 x 102 mm.

Moving decimal 2 places to the left

Hence, the total thickness of the stack is 1.0008 x IQ2 mm.

Exponents And Powers Multiple-Choice Question And Solutions

Question 1. am x an is equal to

  1. am+n
  2. am-n
  3. amn
  4. an-m

Solution: 1. am+n

Question 2. am ÷ am is equal to

  1. am+n
  2. am-n
  3. amn
  4. an-m

Solution: 1. am+n

Question 3. (am)is equal to

  1. am+n
  2. am-n
  3. amn
  4. an-m

Solution: 3. amn

Question 4. Am x is equal to

  1. (ab)m
  2. (ab)-m
  3. amb
  4. abm

Solution: 1. (ab)m

Question 5. a0 is equal to

  1. 0
  2. 1
  3. -1
  4. a

Solution: 2. 1

Question 6. \(\frac{a^m}{b^m}\) is equal to

  1. \(\left(\frac{a}{b}\right)^m\)
  2. \(\left(\frac{b}{a}\right)^m\)
  3. \(\frac{a^m}{b}\)
  4. \(\frac{a}{b^m}\)

Solution: 1. \(\left(\frac{a}{b}\right)^m\)

Question 7. 2 x 2 x 2 x 2 x 2 is equal to

  1. 24
  2. 23
  3. 22
  4. 25

Solution: 4. 25

Question 8. In 102, the exponents

  1. l
  2. 2
  3. 10
  4. 1

Solution: 2. 2

Question 9. In 102, the base is

  1. 1
  2. 0
  3. 10
  4. 100

Solution: 3. \(\frac{1}{10}\)

Question 10. 10-1 is equal to

  1. 10
  2. -1
  3. \(\frac{1}{10}\)
  4. \(-\frac{1}{10} \text {. }\)

Solution: 3. \(\frac{1}{10}\)

Question 11. The multiplicative inverse of 2-3 is

  1. 2
  2. 3
  3. -3
  4. 23

Solution: 4. 23

Question 12. The multiplicative inverse of 105 is

  1. 5
  2. 10
  3. 10-5
  4. 105

Solution: 3. 10-5

Question 13. The multiplicative inverse of \( \frac{1}{2^2}\)

  1. 2-2
  2. 22
  3. 2
  4. 1

Solution: 2. 22

Question 14. The multiplicative inverse of 10 “10 is

  1. 10
  2. \(\frac{1}{10}\)
  3. 10-10
  4. 1010

Solution: 4. 1010

Question 15. The multiplicative inverse of am is

  1. a
  2. m
  3. am
  4. a-m

Solution: 5. a-m

Question 16. 53 x 5-1 is equal to

  1. 5
  2. 53
  3. 5-1
  4. 52

Solution: 4. 52

Question 17. (-2)5 x (- 2)6 is equal to

  1. 2
  2. -2
  3. -5
  4. 6

Solution: 2. -2

Question 18. 32 x 3-4 x 35 is equal to

  1. 3
  2. 32
  3. 33
  4. 35

Solution: 3. 33

19. (- 2) 2 is equal to

  1. \(\frac{1}{4}\)
  2. \(\frac{1}{2}\)
  3. \(-\frac{1}{2}\)
  4. \(-\frac{1}{4}\)

Solution: 1. \(\frac{1}{4}\)

Question 20. \(\left(\frac{1}{2}\right)^{-4}\) is equal to

  1. 2
  2. 24
  3. 1
  4. 2-4

Solution: 2. 24

Question 21. (20 + 4-1) x 22 is equal to

  1. 2
  2. 3
  3. 4
  4. 5

Solution: 4. 5

Question 22. (2-1 + 3-1 + 5-1)0 is equal to

  1. 2
  2. 3
  3. 5
  4. 1

Solution: 4. 1

Question 23. 3m÷ 3-3 = 35 ⇒ m is equal to

  1. 1
  2. 2
  3. 3
  4. 4

Solution: 2. 2

Question 24. (-2)m+1 x (-2)4 = (- 2)6 ⇒ m =

  1. 0
  2. 1
  3. -1
  4. none of these

Solution: 2. 1

Question 25. (-1)60 is equal to

  1. -1
  2. 1
  3. 50
  4. -50

Solution: 2. 1

Question 26. (-1)51 is equal to

  1. -1
  2. 1
  3. 51
  4. -51

Solution: 1. -1

Question 27. 149600000000 is equal to

  1. 1.496 x 1011
  2. 1.496 x lO10
  3. 1.496 x 1012
  4. 1.496 x 105

Solution: 1. 1.496 x 1011

Question 28. 300000000 is equal to

  1. 3 x 108
  2. 3 x 107
  3. 3 x 106
  4. 3 x 109

Solution: 1. 3 x 108

Question 29. 0.000007 is equal to

  1. 7 x 10-6
  2. 7 x 10-6
  3. 7 x 10-4
  4. 7 x 10-3

Solution: 1. 7 x 10-6

Question 30. 384467000 is equal to

  1. 3.84467 x 1o8
  2. 3.84467 x 103
  3. 3.84467 x 107
  4. 3.84467 x 106

Solution: 1. 3.84467 x 108

Question 31. 0.00001275 is equal to

  1. 1.275 x 10-6
  2. 1.275 x 10-3
  3. 1.275 x 104
  4. 1.275 x 103

Solution: 1. 1.275 x 10-6

Question 32. 695000 is equal to

  1. 6.95 x 105
  2. 6.95 x 103
  3. 6.95 x 106
  4. 6.95 x 104

Solution: 1. 6.95 x 105

Question 33. 503600 is equal to

  1. 5.036 x 105
  2. 5.036 x 106
  3. 5.036 x 104
  4. 5.036 x 107

Solution: 1. 5.036 x 105

Question 34. 0.0016is equal to

  1. 1.6 x 10 -3
  2. 1.6 x 10-2
  3. 1.6 x 10 -4
  4. 1.6 x lO-5

Solution: 1. 1.6 x 10-3

Question 35. 0.000003 is equal to

  1. 3 x 10-6
  2. 3 x 106
  3. 3 x 105
  4. 3 x 10-5

Solution: 1. 3 x 10-6

Question 36. 8848 is equal to

  1. 8.848 x 103
  2. 8.848 x 102
  3. 8.848 x 10
  4. 8.848 x 104

Solution: 1. 8.848 x 103

Question 37. 1.5 x 1011 is equal to

  1. 150000000000
  2. 15000000000
  3. 1500000000
  4. 1500000000000

Solution: 1. 150000000000

Question 38. 2.1 x 10-6 is equal to

  1. 0.0000021
  2. 0.000021
  3. 0.00021
  4. 0.0021.

Solution: 1. 0.0000021

Question 39. 2.5 x 104 is equal to

  1. 25
  2. 250
  3. 2500
  4. 25000

Solution: 4. 25000

Question 40. 0.07 x 1O10is equal to

  1. 700000000
  2. 7000000
  3. 7000
  4. 7

Solution: 1. 700000000

Exponents And Powers True-False

Write whether the following statements are True or False:

1. The value of \(\left\{(-1)^{-1}\right\}^{-1}\) is 1: False

2. The reciprocal of \(\left(\frac{4}{3}\right)^0\) is 1: True

3. The standard form of \(\frac{1}{1000000}\) is 1.0 x 10 -6: True

4. If 6m + 6 “3 = 66, then the value of m is 3: True

5. 2345.6 = 2 x 1000 + 3 x 100 + 4 x 10 + 5 x 1 + 6 x 10 – 1: True

Exponents And Powers Fill in the Blanks

1. (1000)° = 1

2. The standard form of 1,234,500,000,000 is: 1.2345 x 1012

3. The multiplicative inverse of(-3) ~2 is: (-3)2

4. (- 9)4 -5- (- 9)10 is equal to (-9)-6

5. The value of (2 -1 + 3 -1 + 4 -1)° is : 1

6. Write 1.0002 x 109 in the usual form: 1000200000

7. Write the reciprocal of 10 _1: 10

8. Find the value of*if* “3 = (100)1-4 + (100)°: 100

9. By what number should (-8) -1 be divided, so that the quotient may be equal to (-8) -1: 1

10. If = \(\frac{5^m \times 5^2 \times 5^{-3}}{5^{-5}}=5^4\) then find the value of m: 0

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