题目内容

脱式计算.
1
2
+
3
5
+
7
10
3
4
-
1
3
-
1
8
1-(
1
2
+
1
3
7
9
-
2
3
+
5
6
19
20
+
1
5
-
9
20
1-
1
14
-
3
7
分析:(1)(2)(4)先通分,在计算;
(3)先算括号内的,再算括号外的;
(5)运用加法交换律与结合律简算;
(6)先通分,运用加法结合律简算.
解答:解:(1)
1
2
+
3
5
+
7
10

=
5
10
+
6
10
+
7
10

=
9
5


(2)
3
4
-
1
3
-
1
8

=
18
24
-
8
24
-
3
24

=
7
24


(3)1-(
1
2
+
1
3

=1-
5
6

=
1
6


(4)
7
9
-
2
3
+
5
6

=
14
18
-
12
18
+
15
18

=
17
18


(5)
19
20
+
1
5
-
9
20

=(
19
20
-
9
20
)+
1
5

=
1
2
+
1
5

=
5
10
+
2
10

=
7
10


(6)1-
1
14
-
3
7

=1-
1
14
-
6
14

=1-(
1
14
+
6
14

=1-
1
2

=
1
2
点评:此题考查了分数的四则混合运算,注意运算顺序和通分计算,同时运用运算定律简算.
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