题目内容
计算下列各题,怎样算简便就怎样算
×
÷
×
(
-
+
)×24
÷〔(
+
)×
〕
2 |
3 |
7 |
5 |
2 |
3 |
7 |
5 |
(
7 |
8 |
5 |
6 |
3 |
4 |
9 |
2 |
1 |
2 |
3 |
4 |
6 |
5 |
考点:分数的四则混合运算,运算定律与简便运算
专题:运算顺序及法则,运算定律及简算
分析:(1)把除法改为乘法,利用乘法交换律与结合律简算;
(2)利用乘法分配律简算;
(3)先算加法,再算乘法,最后算除法.
(2)利用乘法分配律简算;
(3)先算加法,再算乘法,最后算除法.
解答:
解:(1)
×
÷
×
=
×
×
×
=
×
×(
×
)
=
;
(2)(
-
+
)×24
=
×24-
×24+
×24
=21-20+18
=19;
(3)
÷[(
+
)×
]
=
÷[
×
]
=
×
=3.
2 |
3 |
7 |
5 |
2 |
3 |
7 |
5 |
=
2 |
3 |
7 |
5 |
3 |
2 |
7 |
5 |
=
2 |
3 |
3 |
2 |
7 |
5 |
7 |
5 |
=
49 |
25 |
(2)(
7 |
8 |
5 |
6 |
3 |
4 |
=
7 |
8 |
5 |
6 |
3 |
4 |
=21-20+18
=19;
(3)
9 |
2 |
1 |
2 |
3 |
4 |
6 |
5 |
=
9 |
2 |
5 |
4 |
6 |
5 |
=
9 |
2 |
2 |
3 |
=3.
点评:分数四则混合运算的关键是抓住运算顺序,正确按运算书序计算,适当利用运算定律简算.
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