If a train of length $L_1$ km running at a speed of $X$ km/hr crosses a bridge of length $L_2$ km, the time taken is
A$\dfrac{L_1}{X}$ hours
B$\dfrac{L_2}{X}$ hours
C$\dfrac{L_1-L_2}{X}$ hours
D$\dfrac{L_1+L_2}{X}$ hours
Answer & Solution
Correct answer: D. $\dfrac{L_1+L_2}{X}$ hours
While crossing a bridge, the train must clear both its own length and the bridge length. So the total distance covered is $L_1+L_2$, and time is $\frac{L_1+L_2}{X}$ hours.
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