Question

A $100\, m$ long train is moving with a uniform velocity of $45\, km/h$. The time taken by the train to cross a bridge of length $1\, km$ is:

• A. 58 s
• B. 68 s
• C. 78 s
• D. 88 s

Answer 1

Answer: (D)

88 s

Answer 2

Total distance covered by train is sum of train's length plus length of bridge.
Total time taken by train to cross the bridge
$=\frac{\text { Total distance }}{\text { Velocity }}$
Total distance $=$ Length of train $+$ Length of bridge
$=100+1000=1100\, m$
Velocity of train $=45 \,km / h$
$=\frac{45 \times 5}{18}=12.5\, m / s$
$\therefore t=\frac{1100}{12.5}=88\, s$