Multiple choice

A train travels with a speed of 60 kmph from station A to station B and then comes back with a speed of 80 kmph from station B to station A. Find the average speed of the train.

  1. $70\ kmph$
  2. $68.57\ kmph$
  3. $60\ kmph$
  4. $80\ kmph$
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B Correct answer
Explanation

The average speed for a round trip is calculated using the formula 2xy / (x + y), where x and y are the speeds. Here, 2 * 60 * 80 / (60 + 80) = 9600 / 140 = 68.57 kmph.

AI explanation

Since the train covers the same distance in both directions, we use the harmonic mean formula for average speed: 2xy / (x + y). Substituting the speeds of 60 kmph and 80 kmph gives (2 * 60 * 80) / (60 + 80). This simplifies to 9600 / 140, which equals 68.57 kmph.

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