Two swimmers, each 3 km/h in still water, start together from a jetty: one swims upstream, the other downstream. The current is 1 km/h. After 30 minutes both turn and swim back. How much later does the second swimmer reach the jetty than the first?

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Accepted Answer

45 minutes. Upstream swimmer: out 1 km at 2 km/h, back at 4 km/h = 15 min ⇒ 45 min in all. Downstream swimmer: out 2 km at 4 km/h, back at 2 km/h = 1 h ⇒ 1 h 30 min. Difference = 45 minutes.

Two swimmers, each 3 km/h in still water, start together from a jetty: one swims upstream, the other downstream. The current is 1 km/h. After 30 minutes both turn and swim back. How much later does the second swimmer reach the jetty than the first?

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