CA Foundation · Quantitative Aptitude · Measures of Central Tendency and Dispersion
A delivery van travels from Pune to Nashik at 40 km/h and returns over the same distance at 60 km/h. What is its average speed for the whole round trip?
The average speed is 48 km/h. Because the same distance is covered at both speeds, more time is spent at the slower speed, so the harmonic mean 2×40×60/100 = 48 applies, not the arithmetic mean of 50.
- A50 km/h
- B48 km/hCorrect
- C45 km/h
- D52 km/h
Explanation
Equal distances are covered at different speeds, so the harmonic mean applies. Average speed = 2 × 40 × 60 / (40 + 60) = 4800/100 = 48 km/h. The value 50 is the arithmetic mean, which wrongly assumes equal time at each speed.
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