题目内容

(2013?宜丰县模拟)下面各题,怎样简便就怎样算.
19.98×37-199.8×1.9+1998×0.82 9999×7+1111×37
[
8
15
-(
7
12
-
2
5
)]×
15
14
(70+
1
68
)×
1
69
分析:(1)19.98×37-199.8×1.9+1998×0.82,根据因数与积的变化规律将原式转化为:1998×0.37-1998×0.19+1998×0.82,然后运用乘法分配律进行简算;
(2)9999×7+1111×37,根据因数与积的变化规律将原式转化为:1111×63+1111×37,再运用乘法分配律进行简算;
(3)[
8
15
-(
7
12
-
2
5
)]×
15
14
,根据分数四则混合运算的顺序,按照分数四则运算的计算法则进行计算;
(4)(70+
1
68
)×
1
69
,转化为:(69+1+
1
68
)×
1
69
,运用乘法分配律进行简算.
解答:解:(1)19.98×37-199.8×1.9+1998×0.82,
=1998×0.37-1998×0.19+1998×0.82,
=1998×(0.37-0.19+0.82),
=1998×1,
=1998;

(2)9999×7+1111×37,
=1111×63+1111×37,
=1111×(63+37),
=1111×100,
=111100;

(3)[
8
15
-(
7
12
-
2
5
)]×
15
14

=[
8
15
-
11
60
15
14

=
21
60
×
15
14

=
3
8


(4)(70+
1
68
)×
1
69

=:(69+1+
1
68
)×
1
69

=1+
1
69
+
1
68
×
1
69

=1+
1
69
×
(1+
1
68
),
=1+
1
69
×
69
68

=1+
1
68

=1
1
68
点评:此题考查的目的是掌握小数、分数四则混合运算的顺序以及计算法则,并且能够灵活运用简便方法进行计算.
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