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【缘起】五年级上册教学“小数除法”后,练习中常会出现诸如这样的实际问题:“4.5千克黄豆可磨豆腐10千克,磨1千克豆腐需要黄豆多少千克?1千克黄豆可磨豆腐多少千克?”“10千克花生可榨油3.5千克,平均每千克花生可榨油多少千克?榨1千克油需要多少千克花生?”习惯上,我们常把此类问题称为“菜籽榨油”问题。对于小学五年级的学生,他们知道这类题通常可以用除法来解答,但也常常被“究竟应该选择哪个数量作被除数、哪个数量作除
The origin of the fifth grade teaching ”decimal division “ after the practice often appear such as this practical problem: ”4.5 kg of soybeans can tofu 10 kg, mill 1 kg of tofu need soybeans how many kilograms? 1 kg of soybeans can be grinding How many kilograms of tofu? “” 10 kg of peanut oil can be squeezed 3.5 kg, the average number of kilograms of oil per kilogram of peanut oil can be squeezed 1 kg of oil need how many kilograms of peanuts? “Traditionally, we often call such problems ”Rapeseed oil “ problem. For fifth-graders, they know that such questions can usually be solved by division, but they are often ”what exactly should be chosen as the number to be divided and which number to divide