Question

Two trains having lengths of 340 m and 360 m are running at speeds of 80 km/h and 90 km/h, respectively, in the same direction. The time taken (in minutes) by the faster train, coming from behind, to completely cross the other train is:

• A. 7
• B. 4.2
• C. 3.7
• D. 6

Answer 1

Answer:

B. 4.2

Relative speed (same direction)

$90 - 80 = 10 \text{ km/h}$

Convert to m/s:
$10 \times \frac{5}{18} = \frac{50}{18} \text{ m/s}$
Total distance to cross

$340 + 360 = 700 \text{ m}$
Time

$\text{Time} = \frac{700}{50/18} = 700 \times \frac{18}{50} = 252 \text{ seconds}$
Convert to minutes

$252 \div 60 = 4.2 \text{ minutes}$