题目内容
用简便方法计算.
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18×
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1
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分析:(1)(2)(5)(6)运用乘法交换律简算;
(3)(4)按照从左到右的顺序计算.
(3)(4)按照从左到右的顺序计算.
解答:解:(1)
×
×
,
=
×
×
,
=
×
,
=
;
(2)
×
×
,
=
×
×
,
=
×
,
=
;
(3)18×
×
,
=12×
,
=10;
(4)
×
×9,
=
×9,
=2;
(5)
×27×
,
=
×
×27,
=
×27,
=1;
(6)1
×
×
,
=
×
×
,
=
×
,
=
.
5 |
4 |
1 |
2 |
3 |
5 |
=
5 |
4 |
3 |
5 |
1 |
2 |
=
3 |
4 |
1 |
2 |
=
3 |
8 |
(2)
3 |
7 |
1 |
5 |
7 |
9 |
=
3 |
7 |
7 |
9 |
1 |
5 |
=
1 |
3 |
1 |
5 |
=
1 |
15 |
(3)18×
2 |
3 |
5 |
6 |
=12×
5 |
6 |
=10;
(4)
20 |
51 |
17 |
30 |
=
2 |
9 |
=2;
(5)
11 |
36 |
4 |
33 |
=
11 |
36 |
4 |
33 |
=
1 |
27 |
=1;
(6)1
5 |
6 |
2 |
3 |
3 |
22 |
=
11 |
6 |
3 |
22 |
2 |
3 |
=
1 |
4 |
2 |
3 |
=
1 |
6 |
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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