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?

Speed = 9 km/hr = 9 x (5/18) m/sec = 5/2 m/sec

Distance = (35 x 4) m = 140 m.

Time taken = 140 x (2/5) sec= 56 sec