Train [ट्रेन]-02

Question: Two trains 121 meters and 99 meters in length respectively are running in same direction, one at the rate of 40 km and the other at the rate of 32 km an hour .In what time will they be completely clear off each other from the moment they meet?  [Ans. (c) 99 second]

(a) 45 sec (b) 90 sec (c) 99 sec (d) 25 sec (e) None of these

Solution:

Detailed Explanation:

Concept: (1) When two trains passes each other, they describes a distance equal to the sum lengths of both the train.

(2) When two objects are moving in the same direction, then the relative speed of the train is the difference between the speed of the trains.

In the given question, the lengths of the trains are 121 meters and 99 meters, so the distance is (121+99) meters = 220 meters.

Also, the trains are moving in the same directions with the speed of 40 km/h and 32 km/h, so the relative speed = (40-32) km/h = 8 km/h = 8×5/18) m/s = 20/9 m/s

Time = 220 m/(20/9) m/s = 99 sec Ans.