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现行六年制小学课本《数学》第六册17题是这样的:用1、2、3……9,九个数字组成三个数(每个数只能用一次,而且必须要用一次),使其中两个数相减等于第三个数。 这道题按编者的意图是让学生用探索的方法写出一组符合题意的数就行了。但是作为教师则需要知道符合题意的数组究竟有多少?探索出符合题意的数组的成功率有多大?下面就谈谈这个问题。 本文中用字母a、b、c、d、e、f、g、h、i表示九个数字。用abc=100a+bc=100a+10b+c表示由a、b、c
The current six-year primary school textbook “Mathematics” Volume VI 17 is this: with 1,2,3 ... 9, nine numbers form three numbers (each number can only be used once, and must be used once) , Subtract two of them equal to the third number. This question by the editor’s intention is to allow students to use the method of exploration to write a set of questions in line with the number of questions. But as a teacher, you need to know exactly how many arrays match your question, and how big is the success rate of finding an eligible array? The letters a, b, c, d, e, f, g, h, i denote nine numbers in this paper. With abc = 100a + bc = 100a + 10b + c by a, b, c