题目内容
计算下面各题,能简算的要简算.
|
(
|
| ||||||||||||||
2012×
|
|
4×5×(
|
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.
(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)
×
×
,
=
×(
×
),
=
×1,
=
;
(2)(
+
)×24,
=
×24+
×24,
=20+9,
=29;
(3)
×101-
,
=
×(101-1),
=
×100,
=30;
(4)2012×
,
=(2011+1)×
,
=2011×
+1×
,
=2010+
,
=2010
;
(5)
×0.2+0.8×
,
=
×(0.2+0.8),
=
×1,
=
;
(6)4×5×(
-
),
=(4×
×5)-(5×
×4),
=3×5-2×4,
=15-8,
=7.
| 7 |
| 8 |
| 9 |
| 13 |
| 13 |
| 9 |
=
| 7 |
| 8 |
| 9 |
| 13 |
| 13 |
| 9 |
=
| 7 |
| 8 |
=
| 7 |
| 8 |
(2)(
| 5 |
| 6 |
| 3 |
| 8 |
=
| 5 |
| 6 |
| 3 |
| 8 |
=20+9,
=29;
(3)
| 3 |
| 10 |
| 3 |
| 10 |
=
| 3 |
| 10 |
=
| 3 |
| 10 |
=30;
(4)2012×
| 2010 |
| 2011 |
=(2011+1)×
| 2010 |
| 2011 |
=2011×
| 2010 |
| 2011 |
| 2010 |
| 2011 |
=2010+
| 2010 |
| 2011 |
=2010
| 2010 |
| 2011 |
(5)
| 3 |
| 4 |
| 3 |
| 4 |
=
| 3 |
| 4 |
=
| 3 |
| 4 |
=
| 3 |
| 4 |
(6)4×5×(
| 3 |
| 4 |
| 2 |
| 5 |
=(4×
| 3 |
| 4 |
| 2 |
| 5 |
=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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