Calculate the Speed of the Train Crossing a Bridge

What is the speed of the train crossing the bridge?

The train is 100 meters long and completely crosses a 300-meter long bridge in 45 seconds. What is the speed of the train? Is it (a) 32 kmph, (b) 36 kmph, (c) 40 kmph, or (d) 48 kmph?

Speed of the Train Crossing the Bridge

The speed of the train is 40 kmph.

Reflecting on the problem, we need to calculate the speed of the train based on the distance it covers and the time it takes to do so. The train's length is 100 meters, and it completely crosses a 300-meter long bridge in 45 seconds.

To find the speed of the train, we can break down the solution into three steps:

Step 1: Calculate the total distance covered by the train. Since the train crosses both its own length and the length of the bridge, the total distance is 100 meters (train) + 300 meters (bridge) = 400 meters.

Step 2: Calculate the time taken by the train to cover this distance. The information given is that the train crosses the bridge in 45 seconds. Apply the formula for speed: Speed = Distance / Time. Substituting the values, we get Speed = 400 meters / 45 seconds.

Step 3: Converting the speed from meters per second to kilometers per hour, we use the formula Speed (kmph) = (Speed in meters per second) * (18/5). By applying this formula, we get Speed (kmph) = (400/45) * (18/5) ≈ 48 kmph.

Comparing the calculated speed to the options provided, the closest match is 48 kmph, which corresponds to option (d). Therefore, the correct answer is 48 kmph. This problem highlights the importance of understanding speed calculations and converting units for accurate solutions.