A train speeds past a pole in 15 seconds and a platform 100 meter long in 25 seconds What is length ...........

Explanation:

Let the length of the train is x meter and Speed of the train is y meter/second
Then x/y = 15 [because distance/speed = time]
=> y = 15/x

x + 100/25 = x/15

x = 150 mts

So length of the train is 150 meters

Hence, option 3 is the correct answer.