If a man walks at the rate of 4 kmph, he misses a train by only 6 min. However, if he walks at the rate of 5 kmph he reaches the station 6 minutes before the arrival of the train. The distance covered by him to reach the station is Choices:	A) 3 km	B) 4 km	C) 5 km	D) 6 km	E) 7 km

Rationale: let the distance covered be d and time taken to reach the station in time t d / 4 = t + 6 / 60 - - - ( 1 ) d / 5 = t - 6 / 60 - - - ( 2 ) ( 1 ) - ( 2 ) gives d / 4 - d / 5 = ( 6 + 6 ) / 60 d / 20 = 12 / 60 d = 12 * 20 / 60 = 4 km answer : b
Answer: B