Multiple choice

A man travels three equal distances at speeds of 30 km/h, 40 km/h, and 60 km/h, respectively. What is the average speed of the man for the entire journey?

  1. 40 km/h

  2. 42 km/h

  3. 45 km/h

  4. 48 km/h

  5. 50 km/h
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A Correct answer
Explanation

Average speed for equal distances = 3 / (1/30 + 1/40 + 1/60) = 3 / (4/120 + 3/120 + 2/120) = 3 / (9/120) = 3 * 120 / 9 = 40 km/h.

AI explanation

To find the average speed for a journey divided into three equal distances, use the formula 3xyz divided by (xy + yz + zx). Plugging in the speeds of 30 km/h, 40 km/h, and 60 km/h gives 3 multiplied by 72000 as the numerator, which equals 216000. Dividing by the denominator of 1200 plus 2400 plus 1800, which equals 5400, results in an average speed of 40 km/h.

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