Question

A train $150$ meters long and running at a speed of $45$ kmph crossed a bridge in $48$ seconds. Because the train halted on the bridge it took $30$ seconds more to cross the bridge. What is the length of the bridge?

Answer 1

Let, the length of bridge $=xm$.

The speed of the train $=45km/h=\frac{45\times 1000}{3600}m/sec=\frac{25}{2}m/sec$.

Time taken to cross the bridge by train $=(48-30)=18sec$

Since, $time=\frac{distance}{speed}$

$\Rightarrow 18=\frac{150+x}{\frac{25}{2}}$

$\Rightarrow 18\times \frac{25}{2}$ $=150+x$

$\Rightarrow 225-150=x$

$\Rightarrow x=75m$

$\therefore$ length of the bridge $=75m$.