题目内容

(2013?广州模拟)计算下面各题能简便的尽量简便
(1)
8
9
×[
3
4
-(
23
16
-
7
8
)]
(2)9
1
5
+99
1
5
+999
1
5
+9999
1
5
-
4
5
(3)18÷[
5
6
+(
5
8
-
1
3
)]
(4)
1
4
×2003+2005×25%+2004×0.75.
分析:(1)先算小括号里面的减法,再算中括号里面的减法,最后算乘法;
(2)根据加法交换律和结合律进行计算;
(3)先算减法,再算加法,最后算除法;
(4)根据乘法分配律进行计算.
解答:解:
(1)
8
9
×[
3
4
-(
23
16
-
7
8
)]

=
8
9
×[
3
4
-
9
16
],
=
8
9
×
3
16

=
1
6


(2)9
1
5
+99
1
5
+999
1
5
+9999
1
5
-
4
5

=(9+
1
5
)+(99+
1
5
)+(999+
1
5
)+(9999+
1
5
)-
4
5

=(9+99+999+9999)+(
1
5
+
1
5
+
1
5
+
1
5
-
4
5
),
=9+99+999+9999,
=(10-1)+(100-1)+(1000-1)+(10000-1),
=(10+100+1000+10000)-(1+1+1+1),
=11110-4,
=11106;

(3)18÷[
5
6
+(
5
8
-
1
3
)],
=18÷[
5
6
+
7
24
],
=18÷
9
8

=16;

(4)
1
4
×2003+2005×25%+2004×0.75,
=0.25×2003+2005×0.25+2004×(0.25×3),
=0.25×(2003+2005+2004×3),
=0.25×2004×5,
=501×5,
=2505.
点评:此题主要考查分数、小数的四则混合运算的运算顺序和应用运算定律进行简便计算.
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