A train covers a distance in 50 min, if it runs at a speed of 48kmph on an average. The speed at which the train must run to reduce the time of journey to 40min will be.	Choose the correct choice from the following answers.
A) 60 kmph
B) 63 kmph
C) 57 kmph
D) 70 kmph
E) 61 kmph

Rationale: time = 50 / 60 hr = 5 / 6 hr speed = 48 mph distance = s * t = 48 * 5 / 6 = 40 km time = 40 / 60 hr = 2 / 3 hr new speed = 40 * 3 / 2 kmph = 60 kmph answer is a .
Answer: A