Multiple choice

A car travels a certain distance at 24 km/h and comes back at 36 km/h. Find the average speed for total journey.

  1. 28.8 km/hr

  2. 30 km/hr

  3. 27.6 km/hr

  4. 31.2 km/hr
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A Correct answer
Explanation

Average speed = (2 * v1 * v2) / (v1 + v2) = (2 * 24 * 36) / (24 + 36) = (2 * 24 * 36) / 60 = (2 * 24 * 6) / 10 = 288 / 10 = 28.8 km/hr.

AI explanation

When equal distances are travelled at two different speeds, the average speed is given by the formula 2ab/(a+b). Substituting the speeds 24 km/h and 36 km/h gives (2 * 24 * 36) / (24 + 36). The numerator becomes 1728 and the denominator is 60, so dividing 1728 by 60 yields an average speed of 28.8 km/hr.

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