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用减法的性质进行简便计算,学生在理解和运用时都有一定的困难。现就此作一些教法上的探讨。 1.通过学生熟悉的事例说明这种简便计算的原理。例题用9角钱去买4角钱的练习本和2角钱的铅笔,有几种付款方法?还应找回多少钱?学生得出两种解法,即①9角-4角-2角=3角②9角-(4角+2角)=3角再启发学生想想:为什么两种付款方法都对?你觉得哪一种方法更方便?
With the subtraction of the nature of simple calculations, students have some difficulties in understanding and use. Now make some research on the law. 1. Explain the principle of this simple calculation through the familiar examples of students. Examples of 9 dimes to buy 4 dime exercise books and 2 dime pencils, there are several payment methods? How much should be recovered? Students come up with two solutions, namely ①9 angle -4 angle -2 angle = 3 angle ② 9 angle - (4 angle +2 angle) = 3 angle and then inspire students to think about: why two payment methods are right? Which method do you think more convenient?