题目内容

下面各题,怎样简便就怎样算
2
3
+
4
15
×
5
8
 

5
16
×
8
15
-
1
18
5
7
×
4
15
×
7
8
 
12
17
×
5
12
×17 
1
6
×
3
8
×
6
11
5
6
×
7
8
+
5
6
×
1
8
 
3
85
×86
( 
7
9
+
5
27
)×54.
分析:(1)先算乘法,再算加法;
(2)先算乘法,再算减法;
(3)(4)(5)约分计算;
(6)(8)运用乘法分配律简算;
(7)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)
5
16
×
8
15
-
1
18

=
1
6
-
1
18

=
1
9


(3)
5
7
×
4
15
×
7
8
=
1
6


(4)
12
17
×
5
12
×17=5;

(5)
1
6
×
3
8
×
6
11
=
3
88


(6)
5
6
×
7
8
+
5
6
×
1
8

=
5
6
×(
7
8
+
1
8
),
=
5
6
×1,
=
5
6


(7)
3
85
×86,
=
3
85
×(85+1),
=
3
85
×85+
3
85

=3
3
85


(8)(
7
9
+
5
27
)×54,
=
7
9
×54+
5
27
×54,
=42+10,
=52.
点评:此题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.
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