Two trains each 162 m long , moving in opposite directions , cross each other…
2023
Two trains each 162 m long , moving in opposite directions , cross each other in 12 seconds . If one is moving twice as faster the other , then the speed of the faster train is
- A.
30 m/s
- B.
24 m/s
- C.
28 m/s
- D.
18 m/s
Attempted by 22 students.
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Correct answer: D
Answer: 18 m/s
Key idea: When two objects move in opposite directions, add their speeds (relative speed). Use consistent units (meters and seconds) throughout.
Let the speed of the slower train be x m/s. Then the faster train has speed 2x m/s.
Total distance to be covered when they cross = 162 m + 162 m = 324 m.
Relative speed = x + 2x = 3x m/s (since they move in opposite directions).
Use time = distance / relative speed: 324 / (3x) = 12.
Solve for x: 324 = 36x → x = 9 m/s. Therefore the faster train = 2x = 18 m/s.
Quick check: relative speed = 27 m/s, time = 324 / 27 = 12 s, which matches the given time.