题目内容
| 脱式计算，能简算的要简算． (
|
| ||||||||||||||
|
（
|
分析：（2）把除法改为乘法后，都利用乘法分配律简算即可．
解答：解：（1）（
+
-
）×24
=
×24+
×24-
×24
=8+2-4
=6；
（2）
×
+
÷
=
×
+
×
=
×（
+
）
=
；
（3）
×
+
×
=（
+
）×
=1×
=
；
（4）（
+
）×
=
×
+
×
=
+
=
．
| 1 |
| 3 |
| 1 |
| 12 |
| 1 |
| 6 |
=
| 1 |
| 3 |
| 1 |
| 12 |
| 1 |
| 6 |
=8+2-4
=6；
（2）
| 4 |
| 5 |
| 2 |
| 3 |
| 1 |
| 5 |
| 3 |
| 4 |
=
| 4 |
| 5 |
| 2 |
| 3 |
| 1 |
| 5 |
| 4 |
| 3 |
=
| 4 |
| 5 |
| 2 |
| 3 |
| 1 |
| 3 |
=
| 4 |
| 5 |
（3）
| 2 |
| 7 |
| 8 |
| 9 |
| 5 |
| 7 |
| 8 |
| 9 |
=（
| 2 |
| 7 |
| 5 |
| 7 |
| 8 |
| 9 |
=1×
| 8 |
| 9 |
=
| 8 |
| 9 |
（4）（
| 5 |
| 7 |
| 5 |
| 8 |
| 2 |
| 5 |
=
| 5 |
| 7 |
| 2 |
| 5 |
| 5 |
| 8 |
| 2 |
| 5 |
=
| 2 |
| 7 |
| 1 |
| 4 |
=
| 15 |
| 28 |
点评：抓住数字和运算符号的特点，利用选用运算定律简算．
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