Multiple choice

Amol travels from home to college at 40 kmph. On reaching the college gate, he realizes that its Sunday and hence immediately returns home by the same route at 60 kmph. Find his average speed for the entire (to and fro) journey.

  1. 50 kmph

  2. 48 kmph

  3. 45 kmph

  4. 40 kmph
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B Correct answer
Explanation

The average speed for a round trip with speeds v1 and v2 is (2 * v1 * v2) / (v1 + v2). Substituting 40 and 60 gives (2 * 40 * 60) / (40 + 60) = 4800 / 100 = 48 kmph.

AI explanation

Use the harmonic mean formula for equal distances, which is average speed equals 2xy divided by x plus y. Substituting the speeds of 40 kmph and 60 kmph gives 2 multiplied by 40 multiplied by 60 divided by 100. The result is 4800 divided by 100, equaling 48 kmph.

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