题目内容

计算下面各题,能用简便方法计算的用简便方法计算.
41×101                           
7.8+
3
10
+2.2+
7
10
72×(
3
8
+
4
9
)                    
2.5×1.25×32 [1-(
1
5
+
3
10
)]÷
1
4
2
3
-
7
12
)÷(
2
7
+
1
8
分析:(1)(3)运用乘法分配律解答,
(2)运用加法交换律和结合律解答,
(4)化32=4×8,再运用乘法交换律和结合律解答,
(5)(6)依据四则混合运算顺序:先算第二级运算,再算第一级运算,如果只含有同一级运算,按照从左到右顺序计算,有括号先算括号里面的顺序解答.
解答:解:(1)41×101,
=41×100+41×1,
=4100+41,
=4141;

(2)7.8+
3
10
+2.2+
7
10

=(7.8+2.2)+(
3
10
+
7
10
),
=10+1,
=11;

(3)72×(
3
8
+
4
9
),
=72×
3
8
+72×
4
9

=27+32,
=59;

(4)2.5×1.25×32,
=(2.5×4)×(1.25×8),
=10×10,
=100;

(5)[1-(
1
5
+
3
10
)]÷
1
4

=[1-
1
2
1
4

=
1
2
÷
1
4

=2;

(6)(
2
3
-
7
12
)÷(
2
7
+
1
8
),
=
1
12
÷
23
56

=
14
69
点评:本题考查知识点:(1)正确选择并运用简便算法解决问题,(2)依据四则运算顺序正确进行计算.
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