Question

A train running at a speed of 30 km/hr passess a 75 m long platform in 15 seconds. How much time will it take to pass a platform of 90 m long?

Answer 1

Let the length of the train be k
Hence distance covered by the train to passes the platform = length of the train + length of the platform
= (x + 75) m
Time taken to pass the platform = 15 seconds
Speed of train = 30 km/hr = (25/3) m/s

x + 75 = 125
x = 125 – 75 = 50
Hence the length of the train is 50 m.

Hence time taken to cross a platform of 90 m long is 16.8 seconds.

Answer 2

It is a intance of direct variation and in this case there is no role of speed as it is constant
So,
75m in 15sec ....then,
90m in x sec
x= 90 × 15 /75
x = 18
Therefore train can pass in 18 sec