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×
4
7
×
3
4
(2)(
3
4
-
2
5
)×40
(3)[12×(
1
2
-
1
3
)]÷
3
5
(4)
7
15
×
4
5
+
7
15
÷5.
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.
解答:解:
(1)28×
4
7
×
3
4

=28×(
4
7
×
3
4
),
=28×
3
7

=12;

(2)(
3
4
-
2
5
)×40,
=
3
4
×40-
2
5
×40,
=30-16,
=14;

(3)[12×(
1
2
-
1
3
)]÷
3
5

=[12×
1
2
-12×
1
3
3
5

=[6-4]÷
3
5

=2÷
3
5

=
10
3


(4)
7
15
×
4
5
+
7
15
÷5,
=
7
15
×
4
5
+
7
15
×
1
5

=
7
15
×(
4
5
+
1
5
),
=
7
15
×1,
=
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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