Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is-

Question

A. 9

B. 9.6

C. 10

D. 10.8

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Correct Answer :

D. 10.8

R e l a t i v e s p e e d = (60 + 40) k m / h r = (100 x \frac{5}{18}) m / s e c = (\frac{250}{9}) m / s e c . D i s \tan c e c o v e r e d i n c r o s \sin g e a c h o t h e r = (140 + 160) m = 300 m . R e q u i r e d t i m e = (300 x \frac{9}{250}) s e c = \frac{54}{5} s e c = 10.8 s e c .