- A30 minutes
- B15 minutes
- C1 hour
- DNo extra time
Step-by-Step Solution
Lake: 30 ÷ 4 = 7.5 km/h. River: 15/10 + 15/5 = 1.5 + 3 = 4.5 h. Extra = 30 minutes.
Answer: A) 30 minutes
A boat completes a 30 km round trip (15 km out, 15 km back) on a calm lake in 4 hours. How much longer will the same round trip take on a river flowing at 2.5 km/h?
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