题目内容

口算
1
2
-
1
3
=
8
21
+8+
8
21
=
6
5
-
4
5
+
1
5
=
1
3
+
1
4
=		 3-
1
5
-
4
5
=		 3-
1
4
+
1
4
=
1
2
+
1
5
=		 1-
5
8
-
1
8
=		 1+
1
12
+
1
3
=
分析：根据分数加减法的计算方法进行计算．
8
21
+8+
8
21
根据加法交换律进行计算；
3-
1
5
-
4
5
，1-
5
8
-
1
8
根据连减的性质进行计算．
解答：解：
1
2
-
1
3
=
1
6
，
8
21
+8+
8
21
=8
16
21
，
6
5
-
4
5
+
1
5
=
3
5
，
1
3
+
1
4
=
7
12
，		 3-
1
5
-
4
5
=2，		 3-
1
4
+
1
4
=3，
1
2
+
1
5
=
7
10
，		 1-
5
8
-
1
8
=
1
4
，		 1+
1
12
+
1
3
=1
5
12
．
点评：口算时，注意运算符号和数据，然后再进一步计算．
练习册系列答案
相关题目
口算：
125×8=		 300÷12= 450×20= 300-82=
299+63= 13×4+17×4= 12.6×1000= 81.6÷1000=
2.03×10= 6.6÷100= 63÷7÷9= 101×25=
口算：
125×8=		 300÷12= 450×20= 300-82=
299+63= 13×4+17×4= 63÷7÷9= 101×25=
口算
1
4
+
1
3
=
1
3
-
1
5
=		 1÷
1
9
=
2
27
×9=
12
17
÷12=
2
9
×
3
4
=
3
4
÷
1
6
=		 0÷
3
8
=		 7.8×9+7.8=
5
6
+
4
11
×0=
24×（
3
8
+
5
6
）=		 12×
2
25
-
24
25
=
口算
1
4
×
1
3
=
4
7
÷2=
1
2
÷
1
2
=		 10÷
5
6
=
2
3
×
3
4
=
9
10
÷
1
5
=
1
6
÷6=
8
9
÷4=		 15×
4
5
=		 15÷
1
3
=
3
4
×
2
9
=
2
3
÷
1
2
=
2
5
×
1
2
=
1
2
÷
1
4
=
1
2
×
1
4
=
4
5
÷
1
5
=
3
7
×14=
1
4
÷
1
2
=
1
2
-
1
4
=
4
9
×
3
4
=
5
8
×
2
5
=
1
6
÷
2
3
=
1
2
+
1
4
=
3
5
÷1=
7
15
×5=		 1÷
3
4
=
1
2
÷
1
4
=		 1÷
3
5
=
3
4
×12=
1
5
÷
2
3
=
7
9
×
3
7
=		 1-
3
5
=		 18×
5
6
=		 7÷
7
5
=
1
3
+
1
6
=		 1+
3
5
=
2
9
×
1
4
=
8
3
÷2=
3
5
÷
2
5
=
5
9
÷3=
5
6
×
3
10
=
2
5
÷
1
2
=
8×
1
4
=		 9÷
3
4
=		 30×
1
3
=
4
5
÷2=
5
24
÷
5
6
=
5
8
×
1
2
×0=
1
3
×
3
11
=		 8÷
1
4
=
9
10
÷
3
5
=		 0÷
1
3
÷
1
2
=		 1×
9
11
=
2
5
÷
1
5
=
1
3
÷
1
3
=		 0×
2
9
÷
1
2
=
5
6
×
6
5
=
1
5
÷
1
3
=		 0÷
5
12
=		 1×
1
2
÷
1
2
=

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