Two trains 121m and 99m in length, respectively, are running in opposite directions, one at a speed of 40 km/h and the other at a speed of 32 km/h. In what time will they be completely clear of each other from the moment they meet?

11 sec

Total distance = 121 + 99 = 220 m

Relative speed = 40 + 32  = 72 km/h

72 km/h = 72 × \(\frac{5}{18}\) = 20 m/sec

Total time taken to corss each other = \(\frac{Distance}{Speed}\) 

= \(\frac{220}{20}\)  = 11 sec