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三位数除以两位数的试商,是小学数学教学中的一个重点和难点。本文谈谈三位数被两位数除时商9的规律,供同志们参考。请看下面能整除的几道题: 801÷89=9 684÷76=9702÷78=9 468÷52=9603÷67=9 756÷84=9621÷69=9 495÷55=9 从上面商9的几道题中,我们可以发现:三位数除以两位数商9且能整除时,除数减去被除数前两位数的“差”,总是比除数首位数字大1,而且被除数与除数末位数字的和总是合成10。因此,我们可将商9且整除的规律概括为:“‘差’比除头若大1,两数末位合成10,商9没有余”。
Tri-digit divided by two-digit trial, is a primary school mathematics teaching a key and difficult. This article talked about the three-digit double-digit except when the law 9 for my comrades for reference. Look at the following questions that can be divisible: 801 ÷ 89 = 9 684 ÷ 76 = 9702 ÷ 78 = 9 468 ÷ 52 = 9603 ÷ 67 = 9 756 ÷ 84 = 9621 ÷ 69 = 9 495 ÷ 55 = 9 9, we can find that when dividing the three digits by the two digit quotient 9 and dividing it, the divisor minus the “difference” of the first two digits of the divisor is always 1 greater than the first digit of the divisor and the dividend The sum of the last digit of the divisor is always 10. Therefore, we can generalize the law 9 and the divisibility rule as follows: "'Difference' is greater than the head of a divisor, and the last two of the two are synthesized 10, and there is no more than 9 in the quotient.