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数学竞赛中的有理数计算题目有别于平常的有理数计算题,前者其显著特征是:算式中项数多,数字大或结构较复杂,因此,若采用平常的有理数计算方法——先算乘方,同级运算依次运算,有括号先算括号里面等,则难以奏效,为了帮助参赛者在计算中寻求到简捷的求解方法,本文特举例介绍其几种常用计算技巧,供学习参考。1 拆数凑整 例1 用简便方法计算: 7+97+997+9 997+99 997。 (1999年“希望杯”初一培训题) 解原式=(10-3)+(100-3)+(1000-
The mathematical calculation problem in the mathematical competition is different from the usual rational number calculation problem. The former is characterized by the fact that the number of terms in the formula is large, and the number is large or the structure is more complex. Therefore, if the usual rational number calculation method is used, the calculation is first performed. The calculation of the same level in turn, with parentheses first counting inside the brackets, etc., is difficult to be effective. In order to help participants find a simple solution to the calculations, this article gives an example of several commonly used calculation techniques for reference. 1 Number of splits Example 1 Calculated using a simple method: 7+97+997+9 997+99 997. (The 1999 “Hope Cup” first training title) Solution of the original = (10-3) + (100-3) + (1000-