How long will a boy take to run round a square field of side 35 metres. If he runs at the rate of 9km/hr ?  Choose the correct choice
A) 56 sec
B) 1 minute
C) 45 sec
D) 58 sec
E) 50 sec

Rationale: "speed = 9 km / hr = 9 * 5 / 18 = 5 / 2 m / sec distance = 35 * 4 = 140 m time taken = 140 * 2 / 5 = 56 sec . answer is a"
Answer: A