题目内容
用递等式计算,能简算的要简算. 1÷[ ![]() ![]() ![]() | ![]() ![]() ![]() ![]() | 13![]() ![]() ![]() |
3.5×98+3.5×2 | 7.05-4-1.05 | ![]() ![]() |
解:(1)1÷[
×(
-
)],
=1÷[
×
],
=1÷
,
=4;
(2)
×2
+2
÷1
,
=
×
+
×
,
=
+
,
=
;
(3)13
×
+6
÷16,
=13
×
+6
×
,
=(13
+6
)×
,
=20×
,
=
;
(4)3.5×98+3.5×2,
=3.5×(98+2),
=3.5×100,
=350;
(5)7.05-4-1.05,
=(7.05-1.05)-4,
=6-4,
=2;
(6)
×16-8÷
,
=
×16-8×
,
=(16-8)×
,
=2×
,
=
.
分析:(1)先算小括号内的,再算中括号内,最后算括号外的;
(2)先算乘除,再算加法;
(3)(6)把除法改为乘法,运用乘法分配律简算;
(4)运用乘法分配律的逆运算简算;
(5)运用加法交换律与结合律简算.
点评:此题是考查四则混合运算,注意运算顺序,仔细观察算式的特点,灵活运用一些定律进行简便计算.
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/15.png)
![](http://thumb.1010pic.com/pic5/latex/3724.png)
=1÷[
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
=1÷
![](http://thumb.1010pic.com/pic5/latex/96.png)
=4;
(2)
![](http://thumb.1010pic.com/pic5/latex/5192.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/8.png)
![](http://thumb.1010pic.com/pic5/latex/8.png)
=
![](http://thumb.1010pic.com/pic5/latex/5192.png)
![](http://thumb.1010pic.com/pic5/latex/137.png)
![](http://thumb.1010pic.com/pic5/latex/317.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=
![](http://thumb.1010pic.com/pic5/latex/1231.png)
![](http://thumb.1010pic.com/pic5/latex/1653.png)
=
![](http://thumb.1010pic.com/pic5/latex/217117.png)
(3)13
![](http://thumb.1010pic.com/pic5/latex/1207.png)
![](http://thumb.1010pic.com/pic5/latex/69.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
=13
![](http://thumb.1010pic.com/pic5/latex/1207.png)
![](http://thumb.1010pic.com/pic5/latex/69.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/69.png)
=(13
![](http://thumb.1010pic.com/pic5/latex/1207.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/69.png)
=20×
![](http://thumb.1010pic.com/pic5/latex/69.png)
=
![](http://thumb.1010pic.com/pic5/latex/1180.png)
(4)3.5×98+3.5×2,
=3.5×(98+2),
=3.5×100,
=350;
(5)7.05-4-1.05,
=(7.05-1.05)-4,
=6-4,
=2;
(6)
![](http://thumb.1010pic.com/pic5/latex/15700.png)
![](http://thumb.1010pic.com/pic5/latex/4020.png)
=
![](http://thumb.1010pic.com/pic5/latex/15700.png)
![](http://thumb.1010pic.com/pic5/latex/15700.png)
=(16-8)×
![](http://thumb.1010pic.com/pic5/latex/15700.png)
=2×
![](http://thumb.1010pic.com/pic5/latex/15700.png)
=
![](http://thumb.1010pic.com/pic5/latex/40906.png)
分析:(1)先算小括号内的,再算中括号内,最后算括号外的;
(2)先算乘除,再算加法;
(3)(6)把除法改为乘法,运用乘法分配律简算;
(4)运用乘法分配律的逆运算简算;
(5)运用加法交换律与结合律简算.
点评:此题是考查四则混合运算,注意运算顺序,仔细观察算式的特点,灵活运用一些定律进行简便计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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