The speed of a train is 78 km/h. It crosses a tunnel in 45 s and overtakes a person walking at a speed of 6 km/h, in the same direction, in 15 s. The length (in m) of the tunnel is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 675
Length of train = Relative speed × Time to cross man
Relative speed = S1 - S2 [ in same direction]
Length of train = 72 × 5/18 × 15 = 300 m
Length of train + Tunnel = Speed of train × Time to cross tunnel
⇒ 300 + length of tunnel = 78 × 5/18 × 45 = 975
⇒ Length of tunnel = 675 m