题目内容
下列各题,怎样简便就怎样算.
①
|
②
|
③
|
④
|
分析:(1)根据加法交换律进行计算;
(2)先通分,再计算;
(3)先算括号里面的,再算括号外面的;
(4)根据加法交换律和结合律进行计算.
(2)先通分,再计算;
(3)先算括号里面的,再算括号外面的;
(4)根据加法交换律和结合律进行计算.
解答:解:(1)
-
+
,
=
+
-
,
=1-
,
=
;
(2)
+
+
,
=
+
+
,
=
;
(3)
-(
+
),
=
-
,
=
;
(4)
+
+
+
,
=(
+
)+(
+
),
=2+1,
=3.
| 3 |
| 7 |
| 5 |
| 6 |
| 4 |
| 7 |
=
| 3 |
| 7 |
| 4 |
| 7 |
| 5 |
| 6 |
=1-
| 5 |
| 6 |
=
| 1 |
| 6 |
(2)
| 2 |
| 7 |
| 1 |
| 4 |
| 1 |
| 14 |
=
| 8 |
| 28 |
| 7 |
| 28 |
| 2 |
| 28 |
=
| 17 |
| 28 |
(3)
| 7 |
| 6 |
| 2 |
| 5 |
| 3 |
| 10 |
=
| 7 |
| 6 |
| 7 |
| 10 |
=
| 7 |
| 15 |
(4)
| 9 |
| 8 |
| 3 |
| 7 |
| 7 |
| 8 |
| 4 |
| 7 |
=(
| 9 |
| 8 |
| 7 |
| 8 |
| 3 |
| 7 |
| 4 |
| 7 |
=2+1,
=3.
点评:本题主要考查了学生分数四则运算的计算能力,以及在计算中灵活运用简便算法的能力.
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