回複：回複：回複：I think it is answer.

第二問: on average, how many pumps need repairs at any time?

所有跟帖： 

• 回複：回複：回複：回複：I think it is answer. -jinjing- ♀ (112 bytes) () 06/18/2010 postreply 19:44:07

• we get together. -皆兄弟也- ♂ (0 bytes) () 06/18/2010 postreply 20:11:46

• (19*0+12*1+1*2)/32=7/16, right? -皆兄弟也- ♂ (135 bytes) () 06/18/2010 postreply 20:10:28

• 回複：(19*0+12*1+1*2)/32=7/16, right? -jinjing- ♀ (39 bytes) () 06/18/2010 postreply 20:22:27

• don't say that! it is funny we reached the same point. -皆兄弟也- ♂ (0 bytes) () 06/18/2010 postreply 21:53:14