数学题：某工程队铺一段铁路，原计划每天铺3.2千米，15天完成任务。实际的工作效率是原计划的百分之125，实际用多少天完成任务？(用比例知识解)

数学题解答：这题中，这段铁路的长度是一定的，即每天铺路的米米与天数的乘积是一定的，所以天数与每天铺路米数成反比例。

设实际用x天完成任务。

3.2×125%×x＝3.2×15

x=3.2×15÷3.2÷125%

x=12

答：实际需要12天完成。

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