A 145 m long train crosses a man walking at a speed of 9.5 km/h in the opposite direction in 30 seconds. What is the speed (in km/h) of the train ?

Correct option is B

Given:

Length of train = 145 m

Speed of man = 9.5 km/h (opposite direction)

Time to cross = 30 seconds

Find: Speed of train (in km/h)

Formula Used:

Relative Speed = Distance / Time

Train Speed = Relative Speed − Man Speed (since opposite direction → relative = train + man)

145 m = 0.145 km

30 sec = $$\frac{30}{3600}$$​ = $$\frac1{120}$$​ hour

Solution:

Relative Speed = 0.145 ÷ $$\frac1{120}$$​ = 0.145 × 120 = 17.4 km/h

Train Speed = 17.4 - 9.5 = 7.9 km/h