题目内容
用自己喜欢的方法计算:
|
(
|
81×
| ||||||||||||||||||
|
2-
|
[1-(
|
分析:(1)根据加法交换律和结合律进行简算;
(2)根据乘法分配律进行简算;
(3)根据乘法分配律进行简算;
(4)先算乘法,再算加法;
(5)先算除法,再根据减法的性质进行简算;
(6)先算加法,再算减法,最后算除法.
(2)根据乘法分配律进行简算;
(3)根据乘法分配律进行简算;
(4)先算乘法,再算加法;
(5)先算除法,再根据减法的性质进行简算;
(6)先算加法,再算减法,最后算除法.
解答:解:
(1)
+
+
+
,
=(
+
)+(
+
),
=1+1,
=2;
(2)(
+
)×
,
=
×
+
×
,
=
+
,
=
;
(3)81×
,
=(80+1)×
,
=80×
+1×
,
=79+
,
=79
;
(4)
+
×
,
=
+
,
=1;
(5)2-
÷
-
,
=2-
-
,
=2-(
+
),
=2-2,
=0;
(6)[1-(
+
)]÷
,
=[1-
]÷
,
=
÷
,
=
.
(1)
| 5 |
| 7 |
| 5 |
| 6 |
| 2 |
| 7 |
| 1 |
| 6 |
=(
| 5 |
| 7 |
| 2 |
| 7 |
| 5 |
| 6 |
| 1 |
| 6 |
=1+1,
=2;
(2)(
| 5 |
| 6 |
| 5 |
| 8 |
| 24 |
| 25 |
=
| 5 |
| 6 |
| 24 |
| 25 |
| 5 |
| 8 |
| 24 |
| 25 |
=
| 4 |
| 5 |
| 3 |
| 5 |
=
| 7 |
| 5 |
(3)81×
| 79 |
| 80 |
=(80+1)×
| 79 |
| 80 |
=80×
| 79 |
| 80 |
| 79 |
| 80 |
=79+
| 79 |
| 80 |
=79
| 79 |
| 80 |
(4)
| 3 |
| 5 |
| 1 |
| 2 |
| 4 |
| 5 |
=
| 3 |
| 5 |
| 2 |
| 5 |
=1;
(5)2-
| 6 |
| 13 |
| 9 |
| 26 |
| 2 |
| 3 |
=2-
| 4 |
| 3 |
| 2 |
| 3 |
=2-(
| 4 |
| 3 |
| 2 |
| 3 |
=2-2,
=0;
(6)[1-(
| 1 |
| 4 |
| 3 |
| 8 |
| 1 |
| 4 |
=[1-
| 5 |
| 8 |
| 1 |
| 4 |
=
| 3 |
| 8 |
| 1 |
| 4 |
=
| 3 |
| 2 |
点评:考查了运算定律与简便运算,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.
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