Question

Two trains are moving in opposite directions at speeds of 60 km/h and 110 km/h. The length of one train is 360 m. The time taken by them to cross each other is 21 seconds. The length (in m) of the other train, correct to 2 decimal places, is:

• A. 632.93
• B. 631.66
• C. 630.92
• D. 630.08

Answer 1

Answer:

B. 631.66

Since the trains move in opposite directions, their relative speed is the sum of their speeds.

Convert speeds to m/s

$60 + 110 = 170 \text{ km/h}$
$170 \times \frac{1000}{3600} = 47.2222 \text{ m/s}$
Find total distance covered while crossing

$\text{Distance} = \text{Speed} \times \text{Time}$
$= 47.2222 \times 21 = 991.67 \text{ m}$

This distance equals the sum of the lengths of both trains.

Find length of the other train

$\text{Length of other train} = 991.67 - 360 = 631.67 \text{ m}$

Length of the other train = 631.67 m