1*(1/20+1/12)
=1*2/15
=7,5(小时
一件工作甲单独做二十小时完成乙单独做十二小时完成万甲乙合作需几个小时完成这件工作
一件工作甲单独做二十小时完成乙单独做十二小时完成万甲乙合作需几个小时完成这件工作
数学人气:310 ℃时间:2020-04-14 16:49:49
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