数学题：回收1千克废纸，可生产0.8千克再生纸。四一班有54名学生，每人每天回收1千克废纸，5月份（31天）回收的废纸可生产多少千克的再生纸？

数学题解答：54×1×31×0.8=1339.2（千克）

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