Question
Time is taken by two trains running in opposite
directions to cross a man standing on the platform in 25 seconds and 15 seconds respectively. It took 18 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 = 25x Length of second train = Speed × Time = 15y So, {(25x + 15y)/(x+y)} = 18 ⇒  25x + 15y = 18x + 18y ⇒ 7x = 3y Therefore, x:y = 3:7
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