loveparis wrote:

36. Train A leaves the station traveling at 30 miles per hour. Two hours later train В leaves the same station traveling in the same direction at 40 miles per hour. How far from the station was train A overtaken by train B?

(A) 180

(B) 240

(C) 270

(D) 300

(E) 320

This question tests you on relative speed.

Train A leaves the station traveling at 30 miles/hr. So it covers 30*2 = 60 miles in 2 hrs. After 2 hrs, train B leaves the station. When train B leaves the station, distance between train A and train B is 60 miles since train A has already traveled 60 miles.

Now train B needs to cover up this distance between them by traveling faster than train A. In one hour, train B covers 10 miles more than train A (because train B's speed is 10 miles/hr more than train A's speed). So train B will cover the extra 60 miles in 6 hours.

Train A had traveled for 2 + 6 = 8 hrs before it was overtaken by train B. Hence, it had covered a distance of 8*30 = 240 miles.

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