A 375 m long train crosses a man walking at a speed of 10.2 km/h in the opposite direction in 15 seconds. What is the speed (in km/h) of the train? 

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RPF Constable 2024 Official Paper (Held On: 09 Mar, 2025 Shift 1)
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  1. 77.6
  2. 76.2
  3. 79.8
  4. 77.3

Answer (Detailed Solution Below)

Option 3 : 79.8
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Detailed Solution

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Given:

Length of train (L) = 375 m = 0.375 km

Speed of man (Sm) = 10.2 km/h

Time taken (t) = 15 seconds

Formula used:

Speed of train relative to man = Distance / Time

Relative speed (Sr) = Speed of train (St) + Speed of man (Sm)

Calculation:

Relative speed (Sr) = Distance / Time

⇒ Sr = 375 / 15 = 25 m/s

⇒ Sr = 25 × 18/5 = 90 km/h

Speed of train (St) = Relative speed (Sr) - Speed of man (Sm)

⇒ St = 90 - 10.2

⇒ St = 79.8 km/h

∴ The correct answer is option (3).

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