Multiple choice

The ratio of lengths of Train A and Train B is 2 : 3. The speed of A is 36 km/h and that of B is 54 km/h. They cross each other completely in 10 seconds when travelling in opposite directions. In how much time (in seconds) does Train B cross completely a tunnel of length 450 m?

  1. 35

  2. 38

  3. 42

  4. 40

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let lengths be 2x and 3x. Relative speed = 36+54=90 km/h = 25 m/s. Time to cross = (2x+3x)/25 = 5x/25 = 10s, so x=50. Lengths: A=100m, B=150m. Speed of B = 54 km/h = 15 m/s. Tunnel crossing time = (150+450)/15 = 600/15 = 40 seconds.