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?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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