回复：一个小学四年的题（你不见得会，不服气进来瞧瞧）

来源: leoncql 于 2003-11-06 11:00:00 [] [旧帖] [给我悄悄话] 阅读数 : (381 bytes)

18 seconds (they swimed 90 m) they meet first time. Then they meet every 36 (180 m) seconds. So total is 5 times. Don't make it too complex. Just think: after they meet first time, they start at the same place and the same time. Then they swimed apart till the maximum distance (90 m) and then to the minimum distance 0 m, this means they meet once, and repeat till 3 min finished.



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• I think you are wrong, 2 times -freeman212- ♀ 给 freeman212 发送悄悄话 (57 bytes) () 11/06/2003 postreply 11:28:00

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