Multiple choice

A motorcyclist drives from point A to point B with a uniform speed of $30 km$ $h^{-1}$ and returns back to point A with a uniform speed of $20 km$ $h^{-1}$. Find the average speed of the motorcyclist.

  1. $5 km h^{-1}$
  2. $50 km h^{-1}$
  3. $24 km h^{-1}$
  4. $25 km h^{-1}$
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C Correct answer
Explanation

Average speed = (2 * v1 * v2) / (v1 + v2) = (2 * 30 * 20) / (30 + 20) = 1200 / 50 = 24.

AI explanation

To find the average speed for a round trip where equal distances are traveled at two different speeds, we use the harmonic mean formula: 2 times V1 times V2 divided by V1 plus V2. Substituting the given uniform speeds of 30 km/h and 20 km/h into the formula, we get 2 times 30 times 20 divided by 30 plus 20. This simplifies to 1200 divided by 50, which equals 24. The average speed of the motorcyclist is 24 km per hour.

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