Question
A passenger sitting inside a train travelling at 60 km/h observes that the time taken by the train to cross two bridges is in the ratio 7 : 4. What is the length of the second bridge if the first bridge is 280 meters long?
Solution
Time taken by the passenger to cross the first bridge $t_1 = 280/60$. If L is the required length, $t_2 = L/60$. Dividing, $7/4 = 280/L$, which gives L = 160 meters.
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