Question

A train running at the speed of 90 km/h crosses a 400 m long tunnel in 40 seconds. What is the length of the train (in meters)?

• A. 400
• B. 600
• C. 500
• D. 550

Hint:

Convert speed into meters per second before using distance = speed × time. Total distance is train length plus tunnel length.

Answer 1

The Correct Option is C

Speed of train \(= 90 \text{ km/h} = 90 \times \frac{1000}{3600} = 25 \text{ m/s}\).
Time taken to cross tunnel \(= 40 \text{ s}\).
Let the length of the train be \(L \text{ meters}\). The train covers the length of the tunnel plus its own length while crossing.
Total distance covered \(= 400 + L\) meters.
Using formula: \[ \text{Distance} = \text{Speed} \times \text{Time} \] \[ 400 + L = 25 \times 40 = 1000 \text{ meters} \] \[ L = 1000 - 400 = 600 \text{ meters} \] Wait, the answer calculated is 600 meters which matches option (b). Let's double-check. Recalculation: \[ \text{Speed} = 90 \times \frac{1000}{3600} = 25 \text{ m/s} \] \[ \text{Distance} = \text{Speed} \times \text{Time} = 25 \times 40 = 1000 \text{ m} \] Length of train \(L = 1000 - 400 = 600 \text{ m}\) Hence correct answer is (b) 600 meters, not 500.