10 times!!!

来源: iknow!!! 于 2003-11-06 07:57:00 [] [旧帖] [给我悄悄话] 阅读数 : (301 bytes)

set X = the seconds that A and B first time met

when they meet, the total distance must = 90

so 3X + 2X = 90
x = 18

because they just change the position, so when next time they meet, the time is still 18 seconds, and since 3 minutes = 180 sec,

so 180 / 18 = 10





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• 回复：10 is wrong -yma16- ♀ 给 yma16 发送悄悄话 (311 bytes) () 11/06/2003 postreply 08:39:00

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