文档介绍：混合运算
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 - 37
54 ÷ 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 × 3
7 × 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
7
42
÷ 6
做一做
(13 + 5 )÷ 3
4 ×(14 - 8)
= 18 ÷ 3
= 6
= 4 × 6
= 24
1.
.
= 15 -14
= 1
= 8 × 2
= 16
15 - 7 × 2
(15 - 7 )× 2