Multiple choice

A man goes from A to B at a speed of 20 kmph and comes back to A at a speed of 30 kmph. Find his average speed for the entire journey?

  1. 20kmph

  2. 24kmph

  3. 28kmph

  4. 32kmph

  5. 25kmph
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B Correct answer
Explanation

Average speed for a round trip with speeds v1 and v2 is 2*v1*v2 / (v1 + v2). Here, 2 * 20 * 30 / (20 + 30) = 1200 / 50 = 24 kmph.

AI explanation

When equal distances are traveled at two different speeds, the average speed is calculated using the harmonic mean formula: 2xy divided by (x plus y). Substituting the speeds 20 kmph and 30 kmph gives (2 times 20 times 30) divided by (20 plus 30). This simplifies to 1200 divided by 50, resulting in an average speed of 24 kmph.

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