A train running at 54 km/hr takes 20 sec to cross a platform and 15 sec to pass a man walking in the same direction at a speed of 6 km/hr. Then the length of platform is

A200 meters

B100 meters ✓ Correct

C160 meters

D140 meters

Correct answer: (B) 100 meters

Explanation

The platform is 100 meters long.

54 km/hr = 54 x 5/18 = 15 m/sec.

Train + platform = 15 x 20 = 300 m.

Relative speed to the man = 54 - 6 = 48 km/hr = 13.33 m/sec, so train = 13.33 x 15 = 200 m.

Platform = 300 - 200 = 100 m.

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