Question

A train 120 m long travelling at 45 km/hr overtakes another train travelling in the same direction at 36 km/hr and passes it completely in 80 seconds.Find the length of the SECOND train​

Answer 1

Let the length of second train be x meter.

Relative speed = (90 - 72 ) x 5/18 = 18 x 5/18 = 5 m /sec.

Time =  ( 120 + x )/5

⇒ 50 x 5 = 120 + x

⇒ x = 250 - 120

∴ x = 130.

So the length of second train = 130 m.

In opposite direction

Relative speed = 90 + 72 = 162 x  5/18 = 45 m/sec.

Time taken to cross = 250/45 = 50/9 sec..