A 240 m long train overtakes a man walking at 6 km/h, in the same direction, in 9seconds. How much time (in seconds) will it take to pass a 372 m long tunnel with the same speed?

21.6

Let speed of train = S m/sec

Speed of man = 6 km/h = 6 × \(\frac{5}{18}\) = \(\frac{5}{3}\) m/sec

Relative speed (when moves in same direction ) = (S -\(\frac{5}{3}\)) m/sec

According to question ,

240 = (S -\(\frac{5}{3}\)) × 9

85 = 3S

S = \(\frac{85}{3}\) m/sec

Total distance = 240 + 372 = 612 m

Time = \(\frac{Distance}{ Speed }\)

= \(\frac{612 × }{85}\)

= 21.6 sec