Correct Answer - Option 3 : 70 km/h
Given:
Length of two train = 275 m and 175 m
Faster train overtake slower train in 54 sec
Speed of the slower train = 40 km/h
Formula used:
Speed = Distance/Time
When two objects moves in same direction
Relative speed = a - b
Where a and b are speed of the objects, a > b
To convert m/s into km/h multiply by 18/5
Calculation:
Total length = 275 + 175 = 450
Let the speed of the faster train be x km/h
Relative speed = x - 40
⇒\(\dfrac{450}{54}\) = x - 40
⇒ \(\dfrac{450}{54} \times \dfrac{18}{5}\) = x - 40
⇒ 30 = x - 40
⇒ x = 70 km/h
∴ The speed of the faster train is 70 km/h
