Two trains are moving in opposite directions @100kmph and 120kmph. Their length are 500m and 700m. The time taken by the slower train to cross faster train in second is?  Pick one
A) 15 sec
B) 18.3 sec
C) 19.6 sec
D) 20.4 sec
E) 22.5 sec

Rationale: relative speed = 100 + 120 = 220 * 5 / 18 = 550 / 9 m / s distance covered = 500 + 700 = 1200 m required time = 1200 * 9 / 550 = 19.6 sec answer is c
Answer: C