Question

Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?

Answer 1

Length of each train = 120m

Speed of ist train = 120/10 = 12m/s

Speed of 2nd train = 120/15 = 8m/s

Relative speed = 12+8 = 20 m/s

Required time = 120+120/20 =12 sec