Question

A man sees a train passing a bridge 1 km long. The length of the train is half that of the bridge. If the train clears the bridge in 2 minutes, then the speed of the train in km/hr is

• A. $x=35$
• B. $x=45$
• C. $x=40$
• D. $x=65$

Answer 1

The correct option is B $x=45$


According to the given condition

The total distance that needs to be covered by the train to cross the bridge $=\frac{1}{2}+1$

$=\frac{1+2}{2}$

= $\frac{3}{2}km$

Given that the time taken = 2 minutes when converting into hour we have $\frac{2}{60}=\frac{1}{30}hr$

Let the speed of the train = x km/hr

So, the train will cover x km in one hour.

we have

$\begin{array}{c}Distancecoveredtimetaken\\ \frac{3}{2}kms\frac{1}{30}hr\\ xkm1hr\end{array}$

Cross multiplying we have

$\frac{3}{2}\times 1=x\times \frac{1}{30}$

$\frac{3}{2}=\frac{x}{30}$

$45=x$

Hence the speed of the train = 45 km/hr