Subject: General Aptitude · Chapter: Problems on Trains · Exam: · Marks: · Difficulty:
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is :
(a)1 : 3
(b)3 : 2
(c)3 : 4
(d)None of these
Answer
Answer (as printed): B
Explanation
Let the speed of the two trains be $x \mathrm{m} / \mathrm{sec}$ and $y \mathrm{m} / \mathrm{sec}$ respectively. Then, length of the first train $=27 x$ metres, and length of the second train $=17 y$ metres. $$\begin{aligned} & \therefore \frac{27 x+17 y}{x+y}=23 \\ & \Leftrightarrow 27 x+17 y=23 x+23 y \\ & \Leftrightarrow 4 x=6 y \Leftrightarrow \frac{x}{y}=\frac{3}{2} . \end{aligned}$$