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NCERT Exemplar · Class 7 · Maths

Chapter 11: Exponents and Powers

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

Questions

50 questions
Q21Written answer

Which of the following is not true?

(a) 32 > 23 (b) 43 = 26 (c) 33 = 9 (d) 25 > 5

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Worked solution

Solution:-

(c) 33 = 9

3 × 3 × 3 = 27

Therefore, 27 > 9

Q22Written answer

Which power of 8 is equal to 26?

(a) 3 (b) 2 (c) 1 (d) 4

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Worked solution

Solution:-

(b) 2

26 = 2 × 2 × 2 × 2 × 2 × 2

= 64

82 = 8 × 8 = 64

In questions 23 to 39, fill in the blanks to make the statements true.

Q23Written answer

(-2)31 × (-2)13 = (-2)

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Worked solution

Solution:-

(-2)31 × (-2)13 = (-2)44

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am × an = am+n

(-2)31 × (-2)13 = (-2)31 + 13

= -244

Q24Written answer

(-3)8 ÷ (-3)5 = (-3)

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Worked solution

Solution:-

(-3)8 ÷ (-3)5 = (-3)3

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am ÷ an = am–n , m>n

(-3)8 ÷ (-3)5 = (-3)8-5

= -33

Q25Written answer

(11/15)4 × ( )5 = (11/15)9

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Worked solution

Solution:-

(11/15)4 × (11/15)5 = (11/15)9

We know that,

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am × an = am+n

Therefore, (11/15)4 × (11/15)5 = (11/15)9

Q26Written answer

(-1/4)3 × (-1/4) = (-1/4)11

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Worked solution

Solution:-

(-1/4)3 × (-1/4)8 = (-1/4)11

We know that,

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am × an = am+n

Let us assume missing power be y,

Then, (-1/4)3 × (-1/4)y = (-1/4)11

(-1/4)y = (-1/4)11/(-1/4)3

(-1/4)y = (-1/4)11 – 3

(-1/4)y = (-1/4)8

Q27Written answer

[(7/11)3]4 = (7/11)

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Worked solution

Solution:-

3412

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

(am)n = amn

34(3 × 4)

= (7/11)12

Q28Written answer

(6/13)10 ÷ [(6/13)5]2 = (6/13)

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Worked solution

Solution:-

(6/13)10 ÷ [(6/13)5]2 = (6/13)0

In the given question first consider [(6/13)5]2

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

(am)n = amn

52(5 × 2)

= (6/13)10

Then, (6/13)10 ÷ (6/13)10

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am ÷ an = am–n , m>n

(6/13)10 ÷ (6/13)10 = (6/13)10 – 10

= (6/13)0

Q29Written answer

[(-1/4)16]2 = (-1/4)

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Worked solution

Solution:-

16232

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

(am)n = amn

162(16 × 2)

= (-1/4)32

Q30Written answer

(13/14)5 ÷ ( )2 = (13/14)3

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Worked solution

Solution:-

(13/14)5 ÷ (13/14)2 = (13/14)3

We know that,

For any non-zero integers ‘a’ and ‘b’ and whole numbers m and n,

am ÷ an = am–n , m>n

Therefore, (13/14)5 ÷ (13/14)2= (13/14)5 – 2

= (13/14)3