题目内容

怎样简便就怎样算
1
4
+
3
8
)÷(1-
2
7
)=
6.8×2.5+2.5×3.2=
36÷[(
5
6
×
1
3
)×3]=
2
3
÷
5
4
-
2
3
×
4
5
=
7
8
÷5+
7
8
÷7
=
3
4
×1
2
5
+1.4×
1
4
=
分析:(1)两个括号同时计算,然后算除法;
(2)运用乘法分配律简算:
(3)先去小括号,中括号内约分计算,最后算括号外的;
(4)把除法转化为乘法,发现减号前后算式相等,故结果为0;
(5)把除法转化为乘法,运用乘法分配律简算;
(6)把1
2
5
化为小数,运用乘法分配律简算.
解答:解:(1)(
1
4
+
3
8
)÷(1-
2
7
),
=
5
8
÷
5
7

=
5
8
×
7
5

=
7
8


(2)6.8×2.5+2.5×3.2,
=(6.8+3.2)×2.5,
=10×2.5,
=25;

(3)36÷[(
5
6
×
1
3
)×3],
=36÷[
5
6
×
1
3
×3],
=36÷
5
6

=36×
6
5

=43.2;

(4)
2
3
÷
5
4
-
2
3
×
4
5

=
2
3
×
4
5
-
2
3
×
4
5

=0;

(5)
7
8
÷5+
7
8
÷7,
=
7
8
×
1
5
+
7
8
×
1
7

=
7
8
×(
1
5
+
1
7
),
=
7
8
×
12
35

=
3
10


(6)
3
4
×1
2
5
+1.4×
1
4

=
3
4
×1.4+1.4×
1
4

=(
3
4
+
1
4
)×1.4,
=1×1.4,
=1.4.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.
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