Single correct option
Two trains of lengths 150 m and 100 m take 10 seconds to cross each other when running in opposite directions and 50 seconds when running in the same direction. What is the speed of the faster train?
- A. 60 km/h
- B. 54 km/h
- C. 45 km/h
- D. 36 km/h
Show answer and solution
Answer: (B) 54 km/h
Total length to be covered while crossing = 150 + 100 = 250 m.
Opposite directions: a + b = 250/10 = 25 m/s.
Same direction: a − b = 250/50 = 5 m/s.
So a = 15 m/s and b = 10 m/s. Converting: 15 × 18/5 = 54 km/h (the slower one is 36 km/h — a trap option).
Tip: Relative speed adds for opposite directions and subtracts for the same direction; the distance is always the sum of the two lengths.
Opposite directions: a + b = 250/10 = 25 m/s.
Same direction: a − b = 250/50 = 5 m/s.
So a = 15 m/s and b = 10 m/s. Converting: 15 × 18/5 = 54 km/h (the slower one is 36 km/h — a trap option).
Tip: Relative speed adds for opposite directions and subtracts for the same direction; the distance is always the sum of the two lengths.
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