Question

Time is taken by two trains running in opposite directions to cross a man standing on the platform in 27 seconds and 17 seconds respectively. It took 21 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 = 27x Length of second train = Speed × Time = 17y So, {(27x + 17y)/(x+y)} = 21 ⇒  27x + 17y = 21x + 21y ⇒  6x = 4y Therefore, x:y = 2:3

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