My Cart
Your Cart 0

    Your cart is empty.

  • Total (Amount) ₹0.00
NCERT Exemplar · Class 8 · Maths

Chapter 8: Exponents and Powers

Practice each question, then open the answer or worked solution.

Exercise

180 questions
Q21Written answer

For a non-zero integer x, x7 ÷ x12 is equal to

(a) x5 

(b) x19 

(c) x–5 

(d) x–19

Show solutionHide solution
Worked solution

Ans: Option (c) is correct.

Use law of exponent $\dfrac{{{a^m}}}{{{a^n}}} = {\left( a \right)^{m - n}}$, where a is a non zero integer.

Thus, $\dfrac{{{x^7}}}{{{x^{12}}}} = {x^{7 - 12}} = {x^{ - 5}}$.


Q22Written answer

For a non-zero integer x, (x4)–3 is equal to

(a) x12 

(b) x–12 

(c) x64 

(d) x–64

Show solutionHide solution
Worked solution

Ans: Option (b) is correct.

Use law of exponent ${\left( {{x^m}} \right)^n} = {\left( x \right)^{m \times n}} = {\left( x \right)^{mn}}$, where a is a non zero integer.

Thus, ${\left( {{x^4}} \right)^{ - 3}} = {x^{4 \times \left( { - 3} \right)}} = {x^{ - 12}}$


Q23Written answer

The value of (7–1 – 8–1)–1 – (3–1 – 4–1)–1 is

(a) 44 

(b) 56 

(c) 68 

(d) 12

Show solutionHide solution
Worked solution

Ans: Option (a) is correct.

Use the law of exponent ${a^{ - m}} = \dfrac{1}{{{a^m}}}$, where a is a non zero integer.

Thus, 

${\left( {\dfrac{1}{7} - \dfrac{1}{8}} \right)^{ - 1}} - {\left( {\dfrac{1}{3} - \dfrac{1}{4}} \right)^{ - 1}} = {\left( {\dfrac{{8 - 7}}{{56}}} \right)^{ - 1}} - {\left( {\dfrac{{4 - 3}}{{12}}} \right)^{ - 1}}$

= ${\left( {\dfrac{1}{{56}}} \right)^{ - 1}} - {\left( {\dfrac{1}{{12}}} \right)^{ - 1}} = 56 - 12 = 44$


Q24Written answer

The standard form for 0.000064 is

(a) 64 × 104 

(b) 64 × 10–4 

(c) 6.4 × 105 

(d) 6.4 × 10–5

Show solutionHide solution
Worked solution

Ans: Option (d) is correct.

Given, 0.000064 = 0.64 × 10-4 = 6.4 × 10-5


Q25Written answer

The standard form for 234000000 is

(a) 2.34 × 108 

(b) 0.234 × 109 

(c) 2.34 × 10–8 

(d) 0.234 × 10–9

Show solutionHide solution
Worked solution

Ans: Option (a) is correct.

234000000 = 234 x 106 = 2.34 x 102+6

= 2.34 x 108


Q26Written answer

The usual form for 2.03 × 10–5

(a) 0.203 

(b) 0.00203 

(c) 203000 

(d) 0.0000203

Show solutionHide solution
Worked solution

Ans: Option (d) is correct.

Use the law of exponent ${a^{ - m}} = \dfrac{1}{{{a^m}}}$, where a is a non zero integer.

Thus, 

$2.03 \times {10^{ - 5}} = \dfrac{{2.03}}{{{{10}^5}}} = 0.0000203$


Q27Written answer

${\left( {\dfrac{1}{{10}}} \right)^0}$is equal to

(a) 0

(b) $\dfrac{1}{{10}}$

(c) 1

(d) 10

Show solutionHide solution
Worked solution

Ans: Option (c) is correct.

Use the law of exponent ${a^0} = 1$, where a is a non zero integer.

Thus, 

${\left( {\dfrac{1}{{10}}} \right)^0} = 1$


Q28Written answer

${\left( {\dfrac{3}{4}} \right)^5} \div {\left( {\dfrac{5}{3}} \right)^5}$is equal to

(a) ${\left( {\dfrac{3}{4} \div \dfrac{5}{3}} \right)^5}$

(b) ${\left( {\dfrac{3}{4} \div \dfrac{5}{3}} \right)^1}$

(c) ${\left( {\dfrac{3}{4} \div \dfrac{5}{3}} \right)^0}$

(d) ${\left( {\dfrac{3}{4} \div \dfrac{5}{3}} \right)^{10}}$

Show solutionHide solution
Worked solution

Ans: Option (a) is correct.

Use the law of exponent ${a^m} \div {b^m} = {\left( {a \div b} \right)^m}$, where a is a non zero integer.

Thus, 

${\left( {\dfrac{3}{4}} \right)^5} \div {\left( {\dfrac{5}{3}} \right)^5} = {\left( {\dfrac{3}{4} \div \dfrac{5}{3}} \right)^5}$


Q29Written answer

For any two non-zero rational numbers x and y, x4 ÷ y4 is equal to

(a) (x ÷ y)0 

(b) (x ÷ y)1 

(c) (x ÷ y)4 

(d) (x ÷ y)8

Show solutionHide solution
Worked solution

Ans: Option (c) is correct.

Use the law of exponent ${a^m} \div {b^m} = {\left( {a \div b} \right)^m}$, where a is a non zero integer.

Thus, 

${x^4} \div {y^4} = {\left( {\dfrac{x}{y}} \right)^4} = {\left( {x \div y} \right)^4}$


Q30Written answer

For a non-zero rational number p, p13 ÷ p8 is equal to

(a) p5 

(b) p21 

(c) p–5 

(d) p–19

Show solutionHide solution
Worked solution

Ans: Option (a) is correct.

Use the law of exponent ${a^m} \div {a^n} = {\left( a \right)^{m - n}}$, where a is a non zero integer.

Thus, 

${p^{13}} \div {p^8} = {\left( p \right)^{13 - 8}} = {p^5}$