Multiple choice

Two persons X and Y are walking at speeds of 3.6 km/hr and 5.4 km/hr, respectively. They are both walking in the same direction. A train that runs in the same direction as that of X and Y crosses X in 9.6 seconds and Y in 9.8 seconds. Find the speed of the train in km/hr.

  1. 85.5

  2. 51.0

  3. 75.4

  4. 91.8

  5. 99.3

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

Let train speed be V. Relative speeds are (V - 3.6) and (V - 5.4) km/hr. Convert to m/s: (V-3.6)5/18 and (V-5.4)*5/18. Distance = speed * time: L = (V-3.6)(5/18)9.6 and L = (V-5.4)(5/18)*9.8. Equating these: 9.6(V-3.6) = 9.8(V-5.4) => 9.6V - 34.56 = 9.8V - 52.92 => 0.2V = 18.36 => V = 91.8 km/hr.