题目内容

脱式计算(能简便的要用简便方法计算)
(1)
1
6
+
1
5
+
1
3
(2)
7
12
+
1
6
-
1
4
(3)
8
11
+
7
15
-
8
15
(4)7-(
3
4
-
1
5
)
(5)
4
5
-(
4
15
+
1
3
)
(6)
4
7
+
5
21
-
4
7
+
2
21
分析:(1)(2)(4)(5)依据分数四则运算计算顺序即可解答,
(3)依据减法性质解答,
(6)运用加法交换律和结合律解答.
解答:解:(1)
1
6
+
1
5
+
1
3

=
11
30
+
1
3

=
7
10


(2)
7
12
+
1
6
-
1
4

=
3
4
+
1
4

=1;

(3)
8
11
+
7
15
-
8
15

=
8
11
-
1
15

=
109
165


(4)7-(
3
4
-
1
5
)

=7-
11
20

=6
9
20


(5)
4
5
-(
4
15
+
1
3
)

=
4
5
-
9
15

=
1
5


(6)
4
7
+
5
21
-
4
7
+
2
21

=(
4
7
-
4
7
)+(
5
21
+
2
21
),
=0+
1
3

=
1
3
点评:本题考查知识点:(1)按照四则运算计算顺序正确进行计算,(2)正确运用简便算法解决问题.
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