题目内容

计算下面各题,能简算的要简算.
7
8
×
9
13
×
13
9
5
6
+
3
8
)×24       
3
10
×101-
3
10
2012×
2010
2011
3
4
×0.2+0.8×
3
4
4×5×(
3
4
-
2
5
分析:(1)运用乘法结合律简算;
(2)(3)(5)(6)运用乘法分配律简算;
(4)先把2012分解成(2011+1)再运用乘法分配律简算.
解答:解:(1)
7
8
×
9
13
×
13
9

=
7
8
×(
9
13
×
13
9
),
=
7
8
×1,
=
7
8


(2)(
5
6
+
3
8
)×24,
=
5
6
×24+
3
8
×24,
=20+9,
=29;

(3)
3
10
×101-
3
10

=
3
10
×(101-1),
=
3
10
×100,
=30;

(4)2012×
2010
2011

=(2011+1)×
2010
2011

=2011×
2010
2011
+1×
2010
2011

=2010+
2010
2011

=2010
2010
2011


(5)
3
4
×0.2+0.8×
3
4

=
3
4
×(0.2+0.8),
=
3
4
×1,
=
3
4


(6)4×5×(
3
4
-
2
5
),
=(4×
3
4
×5)-(5×
2
5
×4),
=3×5-2×4,
=15-8,
=7.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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