Question

A train crosses a pole in 12 sec, and a bridge of length 170 m in 36 sec. Then the speed of the train is:

A 10.8 km/h Correct Answer Incorrect Answer
B 30.75 km/h Correct Answer Incorrect Answer
C 25.5 km/h Correct Answer Incorrect Answer
D 32.45 km/h Correct Answer Incorrect Answer

Solution

Let the speed of train be s m/sec and length be l. A train crosses a pole in 12 sec. Distance = speed time l = 12s ---(1) A train crosses a bridge of length 170 m in 36 sec. Total length = l + 170 l + 170 = 36s ----(2) Put the value l in eq (2), 12s + 170 = 36s s = 170/24 = 7.08 m/sec = 7.08 $$\times \frac{18}{5} = 25.5 m/sec Speed of the train is 25.5 m/sec.

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