How many seconds will a boy take to run one complete round around a square field of side 20 metres, if he runs at a speed of 16 km/h?

Correct option is C

Given:

Side of the square field = 20 meters

Speed of the boy = 16 km/h

Formula Used:

Time =$$\frac{\text{Distance}}{\text{Speed}}$$​​

Solution:

Perimeter of the square = 4 × side = 4 × 20 = 80 meters

Speed in m/s =$$\frac{16 \times 1000}{3600} = \frac{16000}{3600} = \frac{40}{9} \text{ m/s}$$​

Time =$$\frac{\text{Distance}}{\text{Speed}} = \frac{80}{\frac{40}{9}} = 80 \times \frac{9}{40} = 18 \text{ seconds}$$​
The boy will take 18 seconds to run one complete round around the square field.