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

The correct option is A

16 sec

Step 1: Given Data

1. The length of the train is$100m$.
2. The length of the tunnel is$300m$.
3. The speed of the train is $90Km/h$=$90\times \frac{5}{18}=25m/s$.

Step 2: Calculating time taken by the train

The 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\tan ce\left(s\right)}{time\left(t\right)}$$\Rightarrow time\left(t\right)=\frac{dis\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 $16sec$