A train travelling at a speed of 75 mph enters a tunnel 3 $\dfrac{1}{2}$ miles long. The train is $\dfrac{1}{4}$ mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?
2.5 min
3 min
3.2 min
3.5 min
Explanation:
| Total distance covered | =$ \left(\dfrac{7}{2} +\dfrac{1}{4} \right) $miles |
| =$ \dfrac{15}{4} $miles. |
| $\therefore$ Time taken | $ =\left(\dfrac{15}{4\times 75}\right)hrs$ |
| $=\dfrac{1}{20}hrs $ | |
| $ =\left(\dfrac{1}{20}\times 60\right)min.$ | |
| = 3 min. |