题目内容

计算,能简算的要简算.
15
7
-(
8
7
+
9
14
6
7
+(
4
5
-
3
10
7
10
-
1
4
+
3
10
-
3
4
5
12
+(
6
7
+
7
12
) 
7
8
-
1
6
-
5
12
13
12
-
5
6
+
11
24
分析:(1)运用减法的性质简算;
(2)先算括号内的,再算括号外的;
(3)运用加法交换律与结合律简算;
(4)运用加法交换律简算;
(5)(6)通分计算.
解答:解:(1)
15
7
-(
8
7
+
9
14
),
=
15
7
-
8
7
-
9
14

=1-
9
14

=
5
14


(2)
6
7
+(
4
5
-
3
10
),
=
6
7
+
1
2

=
19
14


(3)
7
10
-
1
4
+
3
10
-
3
4

=(
7
10
+
3
10
)-(
1
4
+
3
4
),
=1-1,
=0;

(4)
5
12
+(
6
7
+
7
12
),
=
5
12
+
6
7
+
7
12

=(
5
12
+
7
12
)+
6
7

=1+
6
7

=
6
7


(5)
7
8
-
1
6
-
5
12

=
21
24
-
4
24
-
10
24

=
7
24


(6)
13
12
-
5
6
+
11
24

=
26
24
-
20
24
+
11
24

=
17
24
点评:考查了分数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
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