题目内容

(1)[9
2008
2009
-(8-
1
2009
)]÷2×
1
2

(2)
4.75×
8
19
+14
2
3
×1.1
8.68-0.36+4.32-1.64
分析:(1)把9
2008
2009
拆成9+
2008
2009
,中括号内运用减法的性质以及加法交换律与结合律简算;
(2)把4.75化成假分数,与
8
19
约分;分母部分运用加法交换律与结合率简算.
解答:解:(1)[9
2008
2009
-(8-
1
2009
)]÷2×
1
2

=[9+
2008
2009
-8+
1
2009
)]÷2×
1
2

=[(9-8)+(
2008
2009
+
1
2009
)]÷2×
1
2

=[1+1]÷2×
1
2

=2÷2×
1
2

=1×
1
2

=
1
2


(2)
4.75×
8
19
+14
2
3
×1.1
8.68-0.36+4.32-1.64

=
19
4
×
8
19
+
44
3
×
11
10
(8.68+4.32)-(0.36+1.64)

=
2+
242
15
13-2

=
272
15
11

=
272
165
点评:仔细观察算式特点,灵活运用运算定律或运算技巧,进行简算.
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