Correct Answer - Option 4 : 500 m
Given:
Length of train = 700 m
Speed of train = 72 km/hr
Train crossed the tunnel in 1 minute
Concept used:
To cross the tunnel train needs to travel = Length of train + length of tunnel
Speed × Time = Distance
Calculation:
Length of train = 700 m
Let the length of tunnel be x
Time taken to cross the tunnel = 1 minute = 60 sec.
Speed = 72 kmph = (72 × 5)/18 = 20 m/sec.
To cross the tunnel train needs to travel = Length of train + length of tunnel = 700 + x
Now,
Speed × Time = Distance
20 × 60 = 700 + x
⇒ x = 1200 – 700 = 500
∴ Length of tunnel = 500 m.
