Distance between two stations P and Q is 500 km. A train covers the journey from P to Q at 60 km per hour and returns back to P with a uniform speed of 40 km per hour. Find the average speed of the train during the whole journey

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  1. 28 km per hour
  2. 55 km per hour
  3. 60 km per hour
  4. 48 km per hour

Answer (Detailed Solution Below)

Option 4 : 48 km per hour
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Detailed Solution

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Given:

Distance between two stations P and Q = 500 km

Speed from P to Q (S1) = 60 km/h

Speed from Q to P (S2) = 40 km/h

Formula used:

Average Speed = \(\frac{(2 × S1 × S2)}{(S1 + S2)} \)

Calculation:

Average Speed = \(\frac{(2 × S1 × S2)}{(S1 + S2)} \)

Average Speed = \(\frac{(2 × 60 × 40)}{(60 + 40)} \)  = (120 × 40) / 100

Average Speed = 48 kmph

∴ The correct answer is option (4).

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