Power Play Class 8 Long Question Answer

Power Play Class 8 Long Question Answer

Power Play Class 8 Long Question Answer

Question 1.

In a stack, there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016 mm. What is the total thickness of the stack ?

Solution:

Thickness of one book = 20 mm

∴ Thickness of 5 books = 5 × 20 mm

= 100 mm.

Thickness of 1 sheet of paper = 0.016 mm

Thickness of 5 sheets of paper

= 5 × 0.016 mm

= 0.08 mm.

Total thickness = 100 mm + 0.08 mm

= 100.08 mm

= 1.0008 × 10² mm.

Question 2.

Express the following numbers in standard form:

(i) 5,00,00,000

(ii) 70,00,000

(iii) 3,18,65,00,000

(iv) 3,90,878

(v) 3,9087.8

(vi) 3908.78

Solution:

(i) 50000000 = 5 × 10000000

= 5 × 10⁷.

(ii) 7000000 = 7 × 1000000

= 7 × 10⁶.

(iii) 3186500000 = 3.1865 × 1000000000

= 3.1865 × 10⁹.

(iv) 390878 = 3.90878 × 100000

= 3.90878 × 10⁵.

(v) 39087.8 = 3.90878 × 10000

= 3.90878 × 10⁴.

(vi) 3908.78 = 3.90878 × 1000

= 3.90878 × 10³.

Question 3.

Say true or false- and justify your answer:

(i) 10 × 10¹¹ = 100¹¹

(ii) 2³ > 5²

(iii) 2³ × 3² = 6⁵

(iv) 3⁰ = (1000)⁰

Solution:

(i) L.H.S. = 10 × 10¹¹ = 10¹⁺¹¹ = 10¹²

and R.H.S. = 100¹¹ = (10²)¹¹ = 10^2x11

= 10²².

Thus L.H.S. ≠ R.H.S.

So, statement is false.

(ii) L.H.S. = 2³ = 2 × 2 × 2 = 8

and R.H.S. = 5² = 5 × 5 = 25.

Thus, L.H.S. ≯ R.H.S.

So, statement is false.

(iii) L.H.S. = 2³ × 3² = 8 × 9 = 72,

and R.H.S. = 6 × 6 × 6 × 6 × 6 = 7776.

∴ L.H.S. ≠ R.H.S.

So, statement is false.

(iv) True. Because 3⁰ = 1 and (1000)⁰ = 1

So, L.H.S. = R.H.S.

So, statement is true.