Question

Time is taken by two trains running in opposite directions to cross a man standing on the platform in 36 seconds and 21 seconds respectively. It took 27 seconds for the trains to cross each other. What is the ratio of their speeds?

A 2:3 Correct Answer Incorrect Answer
B 5:7 Correct Answer Incorrect Answer
C 1:3 Correct Answer Incorrect Answer
D 3:7 Correct Answer Incorrect Answer
E 2:1 Correct Answer Incorrect Answer

Solution

Let the speed one train be x m/s and the speed of the second train be y m/s. Length of the first train = Speed × Time = 36x Length of second train = Speed × Time = 21y So, {(36x + 21y)/(x+y)} = 27 ⇒  36x + 21y = 27x + 27y ⇒  9x = 6y Therefore, x:y = 2:3

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