RD Sharma solution class 7 chapter 11 Percentage Exercise 11.4

Exercise 11.4

Page-11.7

Question 1:

Find each of the following:
(i) 7% of Rs 7150
(ii) 40% of 400 kg
(iii) 20% of 15.125 litres
(iv) $3\frac{1}{3}\% \mathrm{of} 90 \mathrm{km}$
(v) 2.5% of 600 metres

Answer 1:

(i)  7% of  Rs. 7150 = (7/100) ​× 7150 = 50050/100 = Rs.  500.50
(ii) 40% of 400 kg = (40/100) ×  400 = 16000/100 = 160 kg
(iii) 20% of 15.125 litres = (20/100) ×  15.125 =  302.5/100 = 3.025 litres
(iv) $3\frac{1}{3}\%=\frac{10}{3\times 100}\times 90=3 \text{km}$
(v) 2.5% of 600 metres = (2.5/100) × 600 = 1500/100 = 15 metres

Question 2:

Find the number whose $12\frac{1}{2}\%$ is 64.

Answer 2:

Let the number be x.

$$\begin{gathered} 12\frac{1}{2}\% \text{of x}=64 \\ \frac{25}{2}÷100 \times \text{ x}=64 \\ \frac{25\times \text{x}}{2\times 100}=64 \\ 25\times \text{x }=64\times 2\times 100 \\ x=\frac{\mathrm{64\times 2\times 100}}{25}=512 \end{gathered}$$

Question 3:

What is the number, $6\frac{1}{4}\%$ of which is 2?

Answer 3:

Let the number be x.
$$\begin{gathered} 6\frac{1}{4}÷100 \text{of x}=2 \\ \frac{25}{4}÷100 \times \text{ x}=2 \\ \frac{25\times \text{x}}{4\times 100}=2 \\ 25\times \text{x }=2\times 4\times 100 \\ x=\frac{2\times 4\times 100}{25}=32 \end{gathered}$$

Question 4:

If 6 is 50% of a number, what is that number?

Answer 4:

Let the number be x. 
   50% of x = 6
⇒ (50/100) × x = 6
⇒ x = 600/50
⇒ x = 12
So, the number is 12.