数学题：一份稿件，甲、乙两人合打5小时完成，甲的工作效率相当于乙的80％，若这稿件由乙完成，需要几小时？

数学题解答：设稿件为1，这便是工作总量，只需求出乙的工效，便可以算出乙单独完成所需的时间。

甲、乙两人合打5小时完成，说明两人的工效和是1/5。

设乙工效为X，则有：

80%X　+　X　=　1/5

X＝1/9

乙的工效是1/9，所以乙单独完成所需的时间是：1　÷　1/9　＝　9　（天）

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