题目内容
(2009?萝岗区)计算.(写出解答过程,能应简便方法的要用简便方法)
(1)28×
|
(2)(
| ||||||||||||
(3)[12×(
|
(4)
|
分析:(1)根据乘法结合律进行计算;
(2)根据乘法分配律进行计算;
(3)根据乘法分配律进行计算;
(4)根据乘法分配律进行计算.
(2)根据乘法分配律进行计算;
(3)根据乘法分配律进行计算;
(4)根据乘法分配律进行计算.
解答:解:
(1)28×
×
,
=28×(
×
),
=28×
,
=12;
(2)(
-
)×40,
=
×40-
×40,
=30-16,
=14;
(3)[12×(
-
)]÷
,
=[12×
-12×
]÷
,
=[6-4]÷
,
=2÷
,
=
;
(4)
×
+
÷5,
=
×
+
×
,
=
×(
+
),
=
×1,
=
.
(1)28×
4 |
7 |
3 |
4 |
=28×(
4 |
7 |
3 |
4 |
=28×
3 |
7 |
=12;
(2)(
3 |
4 |
2 |
5 |
=
3 |
4 |
2 |
5 |
=30-16,
=14;
(3)[12×(
1 |
2 |
1 |
3 |
3 |
5 |
=[12×
1 |
2 |
1 |
3 |
3 |
5 |
=[6-4]÷
3 |
5 |
=2÷
3 |
5 |
=
10 |
3 |
(4)
7 |
15 |
4 |
5 |
7 |
15 |
=
7 |
15 |
4 |
5 |
7 |
15 |
1 |
5 |
=
7 |
15 |
4 |
5 |
1 |
5 |
=
7 |
15 |
=
7 |
15 |
点评:四则运算,先弄清运算顺序,然后再进一步计算,能简算的要简算.
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