题目内容

口算．
1
3
+
1
4
=
1
5
-
1
6
=		 1-
5
8
=
1
4
+
1
5
=
2
7
+
1
3
=		 1-
7
15
=
3
4
-
1
6
=
7
10
-
1
2
=
3
8
-
1
4
=
5
9
-
4
9
=
1
2
-
1
4
=		 1-
13
13
=
分析：通过观察，除了
5
9
-
4
9
外，都是异分母分数的运算，异分母分数的运算，先通分，再计算．
5
9
-
4
9
是同分母分数的计算，同分母分数的计算，只把分子相加减，分母不变．
解答：解：
1
3
+
1
4
=
7
12
1
5
-
1
6
=
1
30
 1-
5
8
=
3
8
1
4
+
1
5
=
9
20
2
7
+
1
3
=
13
21
 1-
7
15
=
8
15
3
4
-
1
6
=
7
12
7
10
-
1
2
=
1
5
3
8
-
1
4
=
1
8
5
9
-
4
9
=
1
9
1
2
-
1
4
=
1
4
 1-
13
13
=0．
点评：掌握同分母和异分母分数运算的法则，是解题的关键．
练习册系列答案
相关题目
口算．
1
3
-
1
4
=		 42÷10%= 1-0.5= 48×12.5%=
9×
1
9
÷9×
1
9
=		 （
1
4
-
1
5
）×20=		 7.2÷0.08= 5÷
5
7
-
5
7
÷5=
口算．
1
3
-
1
4
=		 5-
5
7
=
4
27
×
9
16
=		 2-
2
3
×2=
1
2
-
1
6
=
3
5
+
4
5
=
3
4
+
1
5
=		 12-
3
8
=
4
5
×
3
2
=		 1+
3
2
×
2
3
=
口算．
1
3
-
1
4
=
1
5
-
1
10
=
7
9
×
6
7
=
6
7
÷6=
12
13
×26=
1÷
5
6
=
3
4
÷
1
8
=		 28×
3
4
=
7
8
×
4
7
=
2
5
×99+
2
5
=
14÷
1
5
=		 (
2
3
-
1
2
)×12=		 1÷
1
4
×4=		 15×
1
3
=
1
3
+
2
13
×
13
14
=
口算：
1
3
-
1
4
=
3
4
+
5
6
=
5
8
×
24
25
=		 1÷
2
5
=		 25×10%=
2
5
÷10=		 25%：
1
8
=		 2-
5
12
-
7
12
=
1
6
+
3
4
+
5
6
+
1
4
=
3
5
×
1
16
+
3
5
×
15
16
=

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