题目内容

(2009?静宁县)计算.
(1)55×66÷(11×11)
(2)40.2-4÷80×2.4      
(3)3.5×[6.8-(1.6+3.6÷0.9)]÷84
(4)
1
8
×[
1
2
÷(
3
5
×
10
9
)]
(5)(
1
2
+
1
4
)÷(
4
5
÷4-
1
10
分析:(1)运用除法的性质简算;
(2)先算除法和乘法,再算减法;
(3)先算小括号内的除法,再算小括号内的加法,然后算中括号内的减法,最后算括号外的乘法和除法;
(4)先算小括号内的,再算中括号内的,最后算括号外的;
(5)两个括号同时计算,第二个括号先算除法,再算减法.
解答:解:(1)55×66÷(11×11),
=55×66÷11÷11,
=55÷11×(66÷11),
=5×6,
=30;

(2)40.2-4÷80×2.4,
=40.2-0.05×2.4,
=40.2-0.12,
=40.08;

(3)3.5×[6.8-(1.6+3.6÷0.9)]÷84,
=3.5×[6.8-(1.6+4)]÷84,
=3.5×[6.8-5.6]÷84,
=3.5×1.2÷84,
=4.2÷84,
=0.05;

(4)
1
8
×[
1
2
÷(
3
5
×
10
9
)],
=
1
8
×[
1
2
÷
2
3
],
=
1
8
×[
1
2
×
3
2
],
=
1
8
×
3
4

=
3
32


(5))(
1
2
+
1
4
)÷(
4
5
÷4-
1
10
),
=
3
4
÷(
4
5
×
1
4
-
1
10
),
=
3
4
÷(
1
5
-
1
10
),
=
3
4
÷
1
10

=
3
4
×10,
=
15
2
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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