题目内容
脱式计算,能简算的要简算. (20+
| (
|
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| 2008×
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考点:分数的简便计算
专题:运算定律及简算
分析:(1)根据乘法分配律进行简算;
(2)根据乘法分配律进行简算;
(3)先算乘法,再根据加法结合律进行简算;
(4)根据乘法分配律进行简算;
(5)根据乘法交换律进行简算;
(6)根据乘法分配律进行简算.
(2)根据乘法分配律进行简算;
(3)先算乘法,再根据加法结合律进行简算;
(4)根据乘法分配律进行简算;
(5)根据乘法交换律进行简算;
(6)根据乘法分配律进行简算.
解答:
解:(1)(20+
)×
=20×
+
×
=16+
=16
;
(2)(
-
)×35
=
×35-
×35
=28-5
=23;
(3)
+
×
-
=
+
-
=
+(
-
)
=
+
=
;
(4)
×99+
=
×(99+1)
=
×100
=80;
(5)
×20×8
=
×8×20
=7×20
=140;
(6)2008×
=(2007+1)×
=2007×
+1×
=2006+
=2006
.
5 |
7 |
4 |
5 |
=20×
4 |
5 |
5 |
7 |
4 |
5 |
=16+
4 |
7 |
=16
4 |
7 |
(2)(
4 |
5 |
1 |
7 |
=
4 |
5 |
1 |
7 |
=28-5
=23;
(3)
5 |
7 |
3 |
4 |
5 |
6 |
3 |
8 |
=
5 |
7 |
5 |
8 |
3 |
8 |
=
5 |
7 |
5 |
8 |
3 |
8 |
=
5 |
7 |
1 |
4 |
=
27 |
28 |
(4)
4 |
5 |
4 |
5 |
=
4 |
5 |
=
4 |
5 |
=80;
(5)
7 |
8 |
=
7 |
8 |
=7×20
=140;
(6)2008×
2006 |
2007 |
=(2007+1)×
2006 |
2007 |
=2007×
2006 |
2007 |
2006 |
2007 |
=2006+
2006 |
2007 |
=2006
2006 |
2007 |
点评:考查了运算定律与简便运算,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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