题目内容
用简便方法计算.
(1)72
|
(2)4
| ||||||
(3)1.625×3.2+5.8×1
|
(4)2
|
分析:(1)将原式变成(72+
)×
,再利用乘法的分配律进行解答;
(2)将原式变成4
-(2
×
),再把2
×
变成(2+
)×
,再利用乘法的分配律进行解答,再相减;
(3)将原式变成1
×3.2+5.3×1
-1
×1,再利用乘法的分配律进行解答;
(4)先将原式变成2
+7.25-1.375-6
.再根据加法结合律及连减的性质进行解答.
18 |
23 |
1 |
9 |
(2)将原式变成4
4 |
5 |
4 |
5 |
5 |
4 |
4 |
5 |
5 |
4 |
4 |
5 |
5 |
4 |
(3)将原式变成1
5 |
8 |
5 |
8 |
5 |
8 |
(4)先将原式变成2
3 |
4 |
5 |
8 |
解答:解:(1)72
÷9,
=(72+
)×
,
=72×
+
×
,
=8+
,
=8
;
(2)4
-(2.8÷
),
=4
-(2
×
),
=4
-(2×
+
×
),
=4
-3
,
=1
;
(3)1.625×3.2+5.8×1
-1.625,
=1
×3.2+5.3×1
-1
×1,
=1
×(3.2+5.3-1),
=
×
,
=
;
(4)2
-1.375+7.25-6
,
=2
+7.25-1.375-6
,
=(2
+7
)-(1
+6
),
=10-8,
=2.
18 |
23 |
=(72+
18 |
23 |
1 |
9 |
=72×
1 |
9 |
18 |
23 |
1 |
9 |
=8+
2 |
23 |
=8
2 |
23 |
(2)4
4 |
5 |
4 |
5 |
=4
4 |
5 |
4 |
5 |
5 |
4 |
=4
4 |
5 |
5 |
4 |
4 |
5 |
5 |
4 |
=4
4 |
5 |
1 |
2 |
=1
3 |
10 |
(3)1.625×3.2+5.8×1
5 |
8 |
=1
5 |
8 |
5 |
8 |
5 |
8 |
=1
5 |
8 |
=
13 |
8 |
15 |
2 |
=
195 |
16 |
(4)2
3 |
4 |
5 |
8 |
=2
3 |
4 |
5 |
8 |
=(2
3 |
4 |
1 |
4 |
3 |
8 |
5 |
8 |
=10-8,
=2.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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