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邻居家五年级的小红遇到这样一道计算题:15÷2.5+15÷7.5,她很轻松地用一般的方法解开了,即分别计算15÷2.5和15÷7.5的商,然后求和得到答案。但她困惑于题目的要求:本题可否简便计算?站在学生的角度,让我们一起来帮助小红解惑释疑。(一)是不是可以简便运算,首先想到的是能不能用运算律。初读本题,两个除法运算的被除数都是15,给人的错觉是逆用分配律,即15÷(2.5+7.5)=15÷10=1.5。在短暂的验证之后就发现这样做是不对的。也
Little Red, a neighbor in her fifth grade, encountered such a calculation: 15 ÷ 2.5 + 15 ÷ 7.5. She easily solved it in the usual way, namely, calculating the quotients of 15 ÷ 2.5 and 15 ÷ 7.5 respectively and then summing Get the answer However, she was perplexed by the requirements of the subject: Can the problem be easily calculated? From a student’s point of view, let us work together to help resolve the doubts and doubts. (A) is not easy to operate, the first thought is that we can use the law of operation. The first reading of the subject, the dividend of the two divide operations are 15, gives the illusion of the inverse distribution of the law, that is 15 ÷ (2.5 + 7.5) = 15 ÷ 10 = 1.5. After a short period of verification found that doing so is wrong. and also