题目内容

用你喜欢的方法计算.
7
9
-
2
3
+
5
6
19
20
+
1
5
-
9
20
1-
1
14
-
3
7
15.8-(14.8+
2
3
7
8
-
3
4
+
1
8
3
7
8
-1
4
9
-1
5
9
分析:(1)(2)(3)题,通分计算;
(4)(6)运用减法的性质简算;
(5)运用加法交换律与结合律简算.
解答:解:(1)
7
9
-
2
3
+
5
6

=
14
18
-
12
18
+
15
18

=
17
18


(2)
19
20
+
1
5
-
9
20

=
19
20
+
4
20
-
9
20

=
7
10


(3)1-
1
14
-
3
7

=1-(
1
14
+
6
14
),
=1-
1
2

=
1
2


(4)15.8-(14.8+
2
3
),
=15.8-14.8-
2
3

=1-
2
3

=
1
3


(5)
7
8
-
3
4
+
1
8

=
7
8
+
1
8
-
3
4

=1-
3
4

=
1
4


(6)3
7
8
-1
4
9
-1
5
9

=3
7
8
-(1
4
9
+1
5
9
),
=3
7
8
-3,
=
7
8
点评:此题考查了通分计算,以及运用运算定律或性质简算.
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