二年级数学混合运算3.ppt.ppt

文档介绍：在没有括号的算式里,只有加、减法或只有乘、除法,都要从左往右按顺序运算. 例1 47 – 12 + 5 = = 40 + 5 35 做一做 48 + 16 -3754 ÷ 9 × 7 = 64 -37 = 27 = 6 × 7 = 42 在没有括号的算式里,有乘法和加、减法,都要先算乘法. 例2 6 × 3 + 50 = = 68 50 – 6 × 3 = 50 –= 32 18 + 50 18 做一做 19 + 5 × 37 × 8 -29 = 19 + 15 = 34 = 56 -29 = 27 在没有括号的算式里,有除法和加、减法,都要先算除法. 例3 54 ÷ 6 – 7= = 2 7 + 54 ÷ 6 = 7 + = 16 9– 7 9 做一做 45 ÷ 5 -8 36 + 49 ÷ 7 = 9 -8 = 1 = 36 + 7 = 43 算式里有括号的,要先算括号里的. 例4 9 ×( 3 + 4 ) = 9 × = 63 (60 – 18 )÷ 6 = = 7 742÷ 6 做一做( 13 + 5 )÷ 34 ×(14 -8) = 18 ÷ 3 = 6 = 4 × 6 = 24 1. . = 15 -14 = 1 = 8 × 2 = 16 15 -7 × 2 (15 -7 )× 2