某工程如果由一二三小队合干,要12天.由一三五小队干,要7天.由二四五小队合干,8天.一三四小队合干,要42天.求5个小队合干要几天完成?

问题描述:

某工程如果由一二三小队合干,要12天.由一三五小队干,要7天.由二四五小队合干,8天.一三四小队合干,要42天.求5个小队合干要几天完成?

1/X1+1/X2+1/X3=1/12 一,1/X1+1/X3+1/X5=1/7 二,1/X2+1/X4+1/X5=1/8 三,1/X1+1/X3+1/X4=1/42 四
一+二+三*2+四=1/12+1/7+2/8+1/42=1/2
1/X1+1/X2+1/X3+1/X4+1/X5=1/2÷3=1/6