题目内容

下面各题,怎样简便就怎样算
2
3
+
4
15
×
5
8

3
4
÷
7
8
÷
15
14

4
9
+
2
15
)÷
2
15
5
6
×
7
8
+
5
6
×
1
8
7
9
+
5
27
)×54
3
85
×86.
分析:(1)先算乘法,再算加法;
(2)把除法改为乘法,约分计算;
(3)把除法改为乘法,运用乘法分配律简算;
(4)(5)运用乘法分配律简算;
(6)把86看作(85+1),运用乘法分配律简算.
解答:解:(1)
2
3
+
4
15
×
5
8

=
2
3
+
1
6

=
5
6


(2)
3
4
÷
7
8
÷
15
14

=
3
4
×
8
7
×
14
15

=
4
5


(3)(
4
9
+
2
15
)÷
2
15

=(
4
9
+
2
15
)×
15
2

=
4
9
×
15
2
+
2
15
×
15
2

=
10
3
+1,
=4
1
3


(4)
5
6
×
7
8
+
5
6
×
1
8

=
5
6
×(
7
8
+
1
8
),
=
5
6
×1,
=
5
6


(5)(
7
9
+
5
27
)×54,
=
7
9
×54+
5
27
×54,
=42+10,
=52;

(6)
3
85
×86,
=
3
85
×(85+1),
=
3
85
×85+
3
85

=3+
3
85

=3
3
85
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.
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