题目内容
(2008?高邮市)
简便计算 5.68-1.57-1.43 |
6.9×0.99 | 60×(
|
|
分析:(1)利用减法的简便方法,把1.57+1.43括起来;
(2)把0.99写成1-0.01,再利用乘法分配律的逆运算计算;
(3)利用乘法分配律的逆运算,把60和括号内的分数逐个相乘,再求和或差;
(4)利用乘法分配律,把公因数
提取出来;
(2)把0.99写成1-0.01,再利用乘法分配律的逆运算计算;
(3)利用乘法分配律的逆运算,把60和括号内的分数逐个相乘,再求和或差;
(4)利用乘法分配律,把公因数
3 |
5 |
解答:解:(1)5.68-1.57-1.43
=5.68-(1.57+1.43),
=5.68-3,
=2.68;
(2)6.9×0.99,
=6.9×(1-0.01),
=6.9-6.9×0.01,
=6.9-0.069,
=6.831;
(3)60×(
+
-
),
=60×
+60×
-60×
,
=36+10-16,
=30;
(4)
×
+
×
,
=
×(
+
),
=
×1,
=
.
=5.68-(1.57+1.43),
=5.68-3,
=2.68;
(2)6.9×0.99,
=6.9×(1-0.01),
=6.9-6.9×0.01,
=6.9-0.069,
=6.831;
(3)60×(
3 |
5 |
1 |
6 |
4 |
15 |
=60×
3 |
5 |
1 |
6 |
4 |
15 |
=36+10-16,
=30;
(4)
3 |
5 |
3 |
7 |
3 |
5 |
4 |
7 |
=
3 |
5 |
3 |
7 |
4 |
7 |
=
3 |
5 |
=
3 |
5 |
点评:灵活应用运算定律可使问题简单化.

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