How many seconds will a boy take to run one complete round around a square field of side 42 metres, if he runs at a speed of 12 km/h?

Correct option is C

Given:

Side of square field = 42 metres

Speed of boy = 12 km/h

Formula Used:

Distance around the square = 4 × side of the square

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

Solution:

Distance around the square = 4 × 42 = 168 metres

Convert speed from km/h to m/s:
12 km/h =$$\frac{12 \times 1000}{3600} \text{m/s}$$​​

Time =$$\frac{168}{\frac{12 \times 1000}{3600} } \approx 50.4 \, \text{seconds}$$​​