题目内容

(2008?纳溪区模拟)下面各题怎样简便就怎样算.
(1)
2
5
÷
3
4
÷
1
15

(2)(
3
5
+
1
6
)×
3
7

(3)13.2÷(3.2×3-0.8)
(4)
7
9
÷[(
5
8
-
1
4
)×12].
分析:(1)把除法改为乘法,约分计算即可;
(2)(3)题,按运算顺序计算,先算括号内的,再算括号外的;
(4)按运算顺序计算,先算小括号内的,再算中括号内的,最后算括号外的.
解答:解:(1)
2
5
÷
3
4
÷
1
15

=
2
5
×
4
3
×15,
=8;

(2)(
3
5
+
1
6
)×
3
7

=(
18
30
+
5
30
)×
3
7

=
23
30
×
3
7

=
23
70


(3)13.2÷(3.2×3-0.8),
=13.2÷(9.6-0.8),
=13.2÷8.8,
=1.5;

(4)
7
9
÷[(
5
8
-
1
4
)×12],
=
7
9
÷[
3
8
×12],
=
7
9
÷
9
2

=
7
9
×
2
9

=
14
81
点评:此题重点考查学生对四则混合运算顺序的掌握情况;注意能约分的要先约分.
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