Question
Train ‘A’ can cross a pole in 10 seconds and a 140
metre long platform in 12 seconds. If the ratio of length of train ‘A’ and train ‘B’ is 2:5, respectively, then find the time taken by train ‘B’ to cross a pole with a speed of 20 m/s.Solution
Let the length and speed of the train ‘A’ be ‘l’ metre and ‘s’ m/s, respectively. According to question, l = 10s Also, 12s = 10s + 140 Or, 2s = 140 Or, s = 70 Therefore, length of train ‘A’ = 10s = 700 metres Length of train ‘B’ = 140 × (5/2) = 1750 metres Required time taken = 1750 ÷ 20 = 87.5 second
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