CMA Foundation · Fundamentals of Business Mathematics and Statistics · Measures of Central Tendency and Dispersion
A delivery van of a Pune firm covers a fixed route one way at 40 km/h and returns over the same distance at 60 km/h. What is its average speed for the round trip?
The average speed is 48 km/h. Because equal distances are covered at different speeds, the harmonic mean applies: 2 × 40 × 60 divided by 100 equals 48. The arithmetic mean of 50 km/h is wrong because more time is spent at the slower speed.
- A48 km/hCorrect
- B50 km/h
- C52 km/h
- D45 km/h
Explanation
The distances are equal, so the average speed is the harmonic mean of the speeds: 2 × 40 × 60 / (40 + 60) = 4800/100 = 48 km/h. Check: for a one-way distance of 240 km the total distance is 480 km and the time is 6 + 4 = 10 h, giving 48 km/h. The 50 km/h option comes from using the arithmetic mean, which is wrong because the time spent at each speed differs.
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