A swimmer's speed downstream is 16 km h⁻¹ and upstream is 8 km h⁻¹. Find the swimmer's speed in still water and the river speed, respectively.
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Question

A swimmer's speed downstream is 16 km h⁻¹ and upstream is 8 km h⁻¹. Find the swimmer's speed in still water and the river speed, respectively.

G1 Physics · Accepted Answer

Let swimmer speed in still water be u and river speed be v. Downstream: u+v=16. Upstream: u-v=8. Adding gives 2u=24, so u=12 km h⁻¹. Then v=4 km h⁻¹. Hence option B. The source options are visibly misprinted, so they are corrected here.