CMA Foundation · Fundamentals of Business Mathematics and Statistics · Time and Distance
Ramesh rows 18 km downstream in 2 hours and returns the same 18 km upstream in 3 hours. What is his average speed for the whole round trip?
The round trip covers 36 km in 5 hours, so the average speed is 36 divided by 5, which equals 7.2 km/h. Averaging the two speeds directly would be wrong because the time spent at each speed is different.
- A7.5 km/h
- B7.2 km/hCorrect
- C6 km/h
- D9 km/h
Explanation
Total distance = 18 + 18 = 36 km and total time = 2 + 3 = 5 hours. Average speed = 36/5 = 7.2 km/h. The 7.5 km/h option takes the simple average of 9 and 6 speeds, which is wrong because the times differ.
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