题目内容

(2010?重庆)计算下面各题,能简算和要简算.
4
5
+
1
4
)÷
2
3

12
5
×(
5
6
+
3
4
)    
6.28+5.74+3.72+5.26
4.27×
1
8
+4.73÷8+
1
8

(2.3+2.3+2.3+2.3)×2.5.
分析:(1)(2)先算括号内的,再算括号外的;
(3)运用加法交换律与结合律简算;
(4)把除法改为乘法,运用乘法分配律简算;
(5)把括号内的算是写成2.3×4,然后运用乘法结合律简算.
解答:解:(1)(
4
5
+
1
4
)÷
2
3

=
21
20
×
3
2

=
63
40


(2)
12
5
×(
5
6
+
3
4
),
=
12
5
×
19
12

=
19
5


(3)6.28+5.74+3.72+5.26,
=(6.28+3.72)+(5.74+5.26),
=10+11,
=21;

(4)4.27×
1
8
+4.73÷8+
1
8

=4.27×
1
8
+4.73×
1
8
+
1
8

=(4.27+4.73+1)×
1
8

=10×
1
8

=
5
4


(5)(2.3+2.3+2.3+2.3)×2.5,
=2.3×4×2.5,
=2.3×(4×2.5),
=2.3×10,
=23.
点评:此题是考查四则混合运算,掌握运算顺序,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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