An easy question on trains and bridges for P4–P5, with a step-by-step solution, diagrams and the answer. Common in the Hua Xia Cup's P5 and P6 qualifying rounds and finals; harder ones have two trains passing, or a train wholly inside a tunnel.
The question
A lamp post stands beside the railway.
A train 156 m long passes it at 12 m a second.
From the front reaching the post until the back passes it, how many seconds?
Show the hints (2)
💡Hint 1: The post is thin enough to count as a point. Once the front reaches it, how much further must the train go for the back to pass it?
💡Hint 2: The train only has to travel its own length.
Worked solution
Have a go first, then read the solution step by step.
1.Once the front reaches the post, the train must go its own length more for the back to pass: the front travels 156 m.
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