题目内容

(2012?潮安县三模)
能简便的要简便计算
4
9
÷[
4
5
-(
1
5
+
1
3
)]-
2
3
(7.6-3.6÷2)×1.5           
4
5
-
1
3
÷
7
15
5
7
÷9+
4
7
×
1
9
2
3
+(
5
6
-
3
4
3
8
7
11
÷[
2
5
-(1-
7
10
)]
1
7
+
5
8
×
5
7
+
3
8
45×(
7
9
+
4
15
-0.6)
0.625×0.5+
5
8
+
1
2
×62.5%
分析:(1)先算小括号内的,再算中括号内的,然后算括号外的除法,最后算减法;
(2)先算括号内的除法,再算括号内的减法,最后算括号外的乘法;
(3)先算除法,再算减法;
(4)把除法改为乘法,运用乘法分配律简算;
(5)先算括号内的,再算括号外的除法,最后算加法;
(6)先算小括号内的,再算中括号内的,最后算括号外的;
(7)先算乘法,再算加法;
(8)运用乘法分配律简算;
(9)把分数和百分数化为小数,运用乘法分配律简算.
解答:解:(1)
4
9
÷[
4
5
-(
1
5
+
1
3
)]-
2
3

=
4
9
÷[
4
5
-
8
15
]-
2
3

=
4
9
÷
4
15
-
2
3

=
4
9
×
15
4
-
2
3

=
5
3
-
2
3

=1;

(2)(7.6-3.6÷2)×1.5,
=(7.6-1.8)×1.5,
=5.8×1.5,
=8.7;

(3)
4
5
-
1
3
÷
7
15

=
4
5
-
1
3
×
15
7

=
4
5
-
5
7

=
3
35


(4)
5
7
÷9+
4
7
×
1
9

=
5
7
×
1
9
+
4
7
×
1
9

=(
5
7
+
4
7
)×
1
9

=
9
7
×
1
9

=
1
7


(5)
2
3
+(
5
6
-
3
4
)÷
3
8

=
2
3
+
1
12
÷
3
8

=
2
3
+
1
12
×
8
3

=
2
3
+
2
9

=
8
9


(6)
7
11
÷[
2
5
-(1-
7
10
)],
=
7
11
÷[
2
5
-
3
10
],
=
7
11
÷
1
10

=
7
11
×10,
=
70
11


(7)
1
7
+
5
8
×
5
7
+
3
8

=
1
7
+
25
56
+
3
8

=
27
28


(8)45×(
7
9
+
4
15
-0.6),
=45×
7
9
+45×
4
15
-45×0.6,
=35+12-27,
=20;

(9)0.625×0.5+
5
8
+
1
2
×62.5%,
=0.625×0.5+0.625+0.5×0.625,
=(0.5+1+0.5)×0.625,
=2×0.625,
=1.25.
点评:考查了四则混合运算的运算顺序以及简便计算,注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.
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