题目内容
用递等式计算,能简算的要简算 (1)(
|
(2)(2-
| ||||||||||||||
(3)5
|
(4)[(2
|
分析:(1)运用乘法的分配律进行计算,使计算更加简便.(2)(3)(4)按照分数的四则混合的运算的顺序进行计算,先计算括号内部的,在计算括号外面的.
解答:解(1)(
+
+
)×72,
=72×
+72×
+
×72,
=30+8+27,
=65;
(2)(2-
×
)÷(
+
),
=(2-
)÷(
+
),
=
×
,
=4;
(3)5
-(1
+3
),
=5
-(1
+3
),
=4
-4
,
=
;
(4)[(2
+4.8÷1
)-4
]×1
,
=[(2
+3)-4
]×
,
=[5
-4
]×
,
=
×
,
=1
.
5 |
12 |
1 |
9 |
3 |
8 |
=72×
5 |
12 |
1 |
9 |
3 |
8 |
=30+8+27,
=65;
(2)(2-
3 |
4 |
4 |
5 |
1 |
12 |
4 |
15 |
=(2-
3 |
5 |
5 |
60 |
16 |
60 |
=
7 |
5 |
60 |
21 |
=4;
(3)5
2 |
5 |
5 |
6 |
3 |
10 |
=5
12 |
30 |
25 |
30 |
9 |
30 |
=4
42 |
30 |
34 |
30 |
=
4 |
15 |
(4)[(2
1 |
3 |
3 |
5 |
1 |
6 |
1 |
2 |
=[(2
1 |
3 |
1 |
6 |
3 |
2 |
=[5
2 |
6 |
1 |
6 |
3 |
2 |
=
7 |
6 |
3 |
2 |
=1
3 |
4 |
点评:此题主要考查分数、整数、小数的四则混合运算的运算顺序和应用运算定律进行简便计算.
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