A 450 metre long train crosses a platform in 50 seconds while it crosses a…
2024
A 450 metre long train crosses a platform in 50 seconds while it crosses a signal pole in 21 seconds. What is the length of the platform?
- A.
623 m
- B.
620 m
- C.
621 m
- D.
625 m
Attempted by 15 students.
Show answer & explanation
Correct answer: C
Key idea: use the time to pass a pole to find the train's speed, then use that speed and the time to pass the platform to find the platform length.
Step 1: Find the train's speed. Speed = train length ÷ time to pass pole = 450 ÷ 21 ≈ 21.428571 m/s.
Step 2: Distance covered while crossing the platform = speed × time to cross platform = 21.428571 × 50 ≈ 1071.428571 m.
Step 3: Platform length = total distance covered − train length = 1071.428571 − 450 ≈ 621.428571 m. Rounding to the nearest metre gives 621 m.