2024 · Q9
Train X crosses a man standing on the platform in 24 seconds and train Y crosses a man standing on the platform in 18 seconds. They cross each other while running in opposite directions in 20 seconds. What is the ratio of speed of X to speed of Y?
Elementary MathematicsTime, Speed and Distance
- A1 : 2
- B2 : 3
- C1 : 3
- D3 : 4
Explanation
Let train X have length Lx and speed vx: Lx = 24vx; similarly Ly = 18vy. Crossing each other in opposite directions: (Lx+Ly)/(vx+vy) = 20, so 24vx+18vy = 20vx+20vy. This gives 4vx = 2vy, i.e. vx : vy = 1 : 2 — option A.