- A10 minutes
- B0 minutes
- C20 minutes
- D5 minutes
Step-by-Step Solution
River: 4/4 + 4/8 = 1.5 h. Lake: 8/6 = 1 h 20 min. Extra = 10 minutes — the current never 'cancels out' over a round trip.
Answer: A) 10 minutes
A rower (6 km/h in still water) goes 4 km up a river flowing at 2 km/h and returns. Compared with doing the same 8 km on a still lake, how many extra minutes does the river cost him?
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