10 times!!!

来源: 于 2003-11-06 07:57:00 [旧帖] [给我悄悄话] 本文已被阅读：次

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