题目内容
计算下面各题,注意使计算简便.
![]() ![]() ![]() | ![]() ![]() ![]() ![]() | (![]() ![]() ![]() |
13-13×![]() | (![]() ![]() ![]() ![]() | [![]() ![]() ![]() ![]() |
解:(1)
÷(1-
)×
,
=
÷
×
,
=
×
×
,
=
;
(2)
×
+
÷
,
=
×
+
×
,
=
×(
+
),
=
×1,
=
;
(3)(
-
)÷
,
=(
-
)×8,
=
×8-
×8,
=
-
,
=
;
(4)13-13×
,
=13×(1-
),
=13×
,
=
;
(5)(
+
)×
+
,
=
×
+
×
+
,
=
+
+
,
=
+(
+
),
=
+1,
=1
;
(6)[
-(
-
)]×
,
=[
-
]×
,
=
×
,
=
.
分析:(1)先算括号内的,再算括号外的除法和乘法;
(2)(3)把除法改为乘法,运用乘法分配律简算;
(4)运用乘法分配律简算;
(5)运用乘法分配律计算(
+
)×
,原式变为
+
+
,运用加法结合律简算;
(6)先算小括号内的,再算中括号内的,最后算括号外的.
点评:此题考查了分数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/3662.png)
![](http://thumb.1010pic.com/pic5/latex/36.png)
=
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/42997.png)
![](http://thumb.1010pic.com/pic5/latex/36.png)
=
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/53491.png)
![](http://thumb.1010pic.com/pic5/latex/36.png)
=
![](http://thumb.1010pic.com/pic5/latex/216811.png)
(2)
![](http://thumb.1010pic.com/pic5/latex/335.png)
![](http://thumb.1010pic.com/pic5/latex/6233.png)
![](http://thumb.1010pic.com/pic5/latex/6232.png)
![](http://thumb.1010pic.com/pic5/latex/259.png)
=
![](http://thumb.1010pic.com/pic5/latex/335.png)
![](http://thumb.1010pic.com/pic5/latex/6233.png)
![](http://thumb.1010pic.com/pic5/latex/6232.png)
![](http://thumb.1010pic.com/pic5/latex/335.png)
=
![](http://thumb.1010pic.com/pic5/latex/335.png)
![](http://thumb.1010pic.com/pic5/latex/6233.png)
![](http://thumb.1010pic.com/pic5/latex/6232.png)
=
![](http://thumb.1010pic.com/pic5/latex/335.png)
=
![](http://thumb.1010pic.com/pic5/latex/335.png)
(3)(
![](http://thumb.1010pic.com/pic5/latex/5690.png)
![](http://thumb.1010pic.com/pic5/latex/1302.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
=(
![](http://thumb.1010pic.com/pic5/latex/5690.png)
![](http://thumb.1010pic.com/pic5/latex/1302.png)
=
![](http://thumb.1010pic.com/pic5/latex/5690.png)
![](http://thumb.1010pic.com/pic5/latex/1302.png)
=
![](http://thumb.1010pic.com/pic5/latex/317.png)
![](http://thumb.1010pic.com/pic5/latex/33.png)
=
![](http://thumb.1010pic.com/pic5/latex/155.png)
(4)13-13×
![](http://thumb.1010pic.com/pic5/latex/40906.png)
=13×(1-
![](http://thumb.1010pic.com/pic5/latex/40906.png)
=13×
![](http://thumb.1010pic.com/pic5/latex/7128.png)
=
![](http://thumb.1010pic.com/pic5/latex/71102.png)
(5)(
![](http://thumb.1010pic.com/pic5/latex/215037.png)
![](http://thumb.1010pic.com/pic5/latex/40906.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/15701.png)
=
![](http://thumb.1010pic.com/pic5/latex/215037.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/40906.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/15701.png)
=
![](http://thumb.1010pic.com/pic5/latex/110760.png)
![](http://thumb.1010pic.com/pic5/latex/7130.png)
![](http://thumb.1010pic.com/pic5/latex/15701.png)
=
![](http://thumb.1010pic.com/pic5/latex/110760.png)
![](http://thumb.1010pic.com/pic5/latex/7130.png)
![](http://thumb.1010pic.com/pic5/latex/15701.png)
=
![](http://thumb.1010pic.com/pic5/latex/110760.png)
=1
![](http://thumb.1010pic.com/pic5/latex/110760.png)
(6)[
![](http://thumb.1010pic.com/pic5/latex/2367.png)
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/2405.png)
![](http://thumb.1010pic.com/pic5/latex/68679.png)
=[
![](http://thumb.1010pic.com/pic5/latex/2367.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/68679.png)
=
![](http://thumb.1010pic.com/pic5/latex/3660.png)
![](http://thumb.1010pic.com/pic5/latex/68679.png)
=
![](http://thumb.1010pic.com/pic5/latex/2638.png)
分析:(1)先算括号内的,再算括号外的除法和乘法;
(2)(3)把除法改为乘法,运用乘法分配律简算;
(4)运用乘法分配律简算;
(5)运用乘法分配律计算(
![](http://thumb.1010pic.com/pic5/latex/215037.png)
![](http://thumb.1010pic.com/pic5/latex/40906.png)
![](http://thumb.1010pic.com/pic5/latex/112.png)
![](http://thumb.1010pic.com/pic5/latex/110760.png)
![](http://thumb.1010pic.com/pic5/latex/7130.png)
![](http://thumb.1010pic.com/pic5/latex/15701.png)
(6)先算小括号内的,再算中括号内的,最后算括号外的.
点评:此题考查了分数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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