they go off at the same time at 0, 30, 60, 90, 120, 150, 180, 2

来源: 于 2016-01-22 07:42:24 [旧帖] [给我悄悄话] 本文已被阅读：次

they go off at the same time at  0, 30, 60, 90, 120, 150, 180, 210, 240， 270 and 300.

 

300 is on the 5th min， 该算吗？