对于有理数的混合运算,除了按照运算法则和运算顺序计算外,还需要讲究一些运算技巧,力求使运算简便.进行有理数的乘除混合运算时,若能根据算式的结构特征,选择合理的运算路径,灵活使用运算律,可简化运算过程,提高解题速度和能力.下面举例说明有理数运算中常见一些的技巧.一、先变形,后分组,再相加例1计算138+27-49-996+2006+28.解:原式=(140-2)+(30-3)+(-50+1)+(-1000 For the rational number of mixed operations, in addition to the algorithm and computing sequence in addition to calculating, but also need to pay attention to some computing skills, and strive to make the operation is simple.When the multiplication and division of rational numbers mixed operation, according to the structural characteristics of the formula, choose a reasonable path, Flexibility to use the law of operations, can simplify the process, improve the speed and ability to solve problems. The following examples illustrate some common rational number arithmetic skills. First, deformation, after the group, and then add Example 1 138 + 27-49-996 + 2006 +28. Solution: Original = (140-2) + (30-3) + (- 50 + 1) + (-1000)