题目内容
计算并写出主要过程．
①
+
②
-
③
÷
．
①
| 7 |
| 10 |
| 8 |
| 15 |
②
| 7 |
| 16 |
| 3 |
| 20 |
③
| 5 |
| 24 |
| 7 |
| 36 |
分析：①②先通分再相加减；③根据除以一个数等于乘这个数的倒数求解．
解答：解：①
+
=
+
=
=
；
②
-
=
-
=
=
；
③
÷
，
=
，
=
．
| 7 |
| 10 |
| 8 |
| 15 |
| 21 |
| 30 |
| 16 |
| 30 |
| 21+16 |
| 30 |
| 37 |
| 30 |
②
| 7 |
| 16 |
| 3 |
| 20 |
| 35 |
| 80 |
| 12 |
| 80 |
| 35-12 |
| 80 |
| 23 |
| 80 |
③
| 5 |
| 24 |
| 7 |
| 36 |
=
，=
| 15 |
| 14 |
点评：异分母分数相加减先通分化成同分母分数再计算；分数除法：除以一个数等于乘这个数的倒数求解．
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