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Question

# A 100 m long train moving with a constant speed of 90 $\frac{km}{hr}$ crosses a tunnel of 300 meters long. The time taken by the train to cross the tunnel completely is

A

16 sec

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B

8 sec

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C

4 sec

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D

2 sec

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Solution

## The correct option is A 16 secStep 1: Given DataThe length of the train is$100m$.The length of the tunnel is$300m$.The speed of the train is $90Km/h$=$90×\frac{5}{18}=25m/s$.Step 2: Calculating time taken by the trainThe total distance covered by the train is equal to $lengthofthetrain+lengthofthetunnel$ So distance (s) = $100+300=400$ $m$Now$speed\left(v\right)=\frac{dis\mathrm{tan}ce\left(s\right)}{time\left(t\right)}$$⇒time\left(t\right)=\frac{dis\mathrm{tan}ce\left(s\right)}{speed\left(v\right)}$So $time=\frac{400}{25}$= $16sec$Hence, the time taken by the train to cross the tunnel is $16sec$

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