CMA Foundation · Fundamentals of Business Mathematics and Statistics · Time and Distance
Ravi travels from his office to a client site at 40 km/h and returns along the same route at 60 km/h. What is his average speed for the whole round trip?
The average speed is 48 km/h. For equal distances covered at two speeds, average speed is the harmonic form 2xy/(x+y), giving 2 x 40 x 60 / 100 = 48. Simple averaging to 50 is wrong because more time is spent at the slower speed.
- A48 km/hCorrect
- B50 km/h
- C52 km/h
- D45 km/h
Explanation
For equal distances average speed = 2xy/(x+y) = 2x40x60/100 = 48 km/h. Check with 120 km each way: time = 3 + 2 = 5 h for 240 km gives 48. The 50 km/h option is the arithmetic mean, which is wrong because the times differ.
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