题目内容

(2012?新津县)能用简便方法计算的用简便方法计算.
25×1.25×32 
(3.75+4.1+2.15)×9.8
5400-2940÷28×27
(20.2×0.4+7.88)÷4.2
4
5
+
1
4
)÷
7
3
+
7
10
  
10÷[
8
3
-(
5
13
÷
5
26
+
2
5
)].
分析:只有第一题,25×1.25×32,把32分解为4×8,再根据乘法交换律、结合律进行简算;
其它5道题根据四则混合运算的运算顺序,和小数、分数四则运算的计算法则脱式计算;
解答:解:(1)25×1.25×32,
=(25×4)×(1.25×8),
=100×10,
=1000;

(2)(3.75+4.1+2.15)×9.8,
=10×9.8,
=98;

(3)5400-2940÷28×27,
=5400-105×27,
=5400-2835,
=2565;

(4)(20.2×0.4+7.88)÷4.2,
=(8.08+7.88)÷4.2,
=15.96÷4.2,
=3.8;

(5)(
4
5
+
1
4
)÷
7
3
+
7
10

=
21
20
×
3
7
+
7
10

=
9
20
+
14
20

=
23
20

=1
3
20


(6)10÷[
8
3
-(
5
13
÷
5
26
+
2
5
)],
=10÷[
8
3
-(
5
13
×
26
5
+
2
5
)],
=10÷[
8
3
-(2+
2
5
)],
=10÷[
8
3
-
12
5
],
=10÷[
40
15
-
36
15
],
=10÷
4
15

=10×
15
4

=
75
2

=37
1
2
点评:此题主要考查小数、分数四则混合运算的计算,要注意分析式中数据,运用合适的简便方法计算.
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