数学题：儿童的负重最好不要超过体重的20分之3。如果长期背负过重的物体，会导致腰痛及背痛，严重的甚至会妨碍骨骼生长。小乐的书包超重吗？为什么?(书包重5kg，体重30kg)

数学题解答：超了，5/30大于3/20。

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