有一个被修复的道路.A需要10天完成,B需要十二天和C需要15天.现在他们一起工作,修补道路.A中途离场,最后,他们花了6天完成了道路.A离开后,求有多少天B和C一起工作?
列个方程,很简单的.
设A工作x天,总工作量为1
可得：
（1/10 + 1/12 + 1/15)x +(1/12 + 1/15)(6-x)=1
解得 x=1
所以BC一起工作5天
一道英语奥数题there is a road to be repaired.A needs 10days to fini
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