How long will a boy take to run round a square field of side 35 meters, If he runs at the rate of 9 km/hr?

Question: How long will a boy take to run round a square field of side 35 meters, If he runs at the rate of 9 km/hr?

Solution:
Speed = 9 km/hr = 9 × (5/18) m/sec = 5/2 m/sec

Distance = (35 × 4) m = 140 m.

Time taken = 140 × (2/5) sec= 56 sec