A train 850 m long is running at a speed of 70 km/h. If it crosses a tunnel in $1\frac{1}{2}$ minute, then the length of the tunnel (in m) is
Answer & explanation
Correct answer: option 3
Speed of train = 70 km/h
= 70 × \(\frac{5}{18}\) m/sec
Total time taken to cross the tunnel = 1.5 minute = 90 sec
Total distance to travel = Length of train + Tunnel length
= 850 + Tunnel length
Distance = Speed × Time
850 + Tunnel length = 70 × \(\frac{5}{18}\) × 90
850 + Tunnel length = 1750
Tunnel length = 900
The correct answer is option (3) : 900