Two trains of equal lengths take 10 sec and 8 sec respectively to cross a telegraph post. If the length of each train be 120 m, in what time will they cross other travelling in opposite direction? Choose the correct choice from the following choices: A) 22 B) 12 C) 9 D) 99 E) 21

Rationale: speed of the first train = 120 / 10 = 12 m / sec . speed of the second train = 120 / 8 = 15 m / sec . relative speed = 12 + 15 = 27 m / sec . required time = ( 120 + 120 ) / 27 = 9 sec . answer : c
Answer: C