2025 · Q66
Two trains A and B are entering a railway platform from opposite direction. The length of the platform is 300 m. The speed of B is two times the speed of A. The time taken by B to cross the platform is one-third of the time taken by A to cross the platform. If the sum of the lengths of A and B is 500 m, what is the difference in their lengths?
general-mental-abilityquantitative-aptitude
- A220 m
- B250 m
- C200 m
- D300 m
Explanation
Let the train lengths be La and Lb with La+Lb = 500. Crossing time = (train length + 300)/speed. With vB = 2 vA: (Lb+300)/(2vA) = (1/3)(La+300)/vA, giving 3(Lb+300) = 2(La+300), i.e. 2La - 3Lb = 300. Substituting La = 500 - Lb: 1000 - 5Lb = 300, so Lb = 140 m and La = 360 m. The difference is 220 m.