A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:






Explanation

Let the length of the train be x metres and its speed by y m/sec.

Then, x = 15     =>     y = x .
y 15

Therefore x + 100 = x
25 15

=> 15(x + 100) = 25x

=> 15x + 1500 = 25x

=> 1500 = 10x

=> x = 150 m.