| 序号 | 题目：1,5,9,11 | |
|---|---|---|
| 1 | ((9 − 1) + 5) + 11 | |
| 2 | ((11 − 1) + 5) + 9 | |
| 3 | ((11 + 5) − 1) + 9 | |
| 4 | ((9 + 5) + 11) − 1 | |
| 5 | ((11 + 5) + 9) − 1 | |
| 6 | ((11 + 9) − 1) + 5 | |
| 7 | ((9 + 5) − 1) + 11 | |
| 8 | ((11 + 9) + 5) − 1 | |
| 9 | ((11 − 1) + 9) + 5 | |
| 10 | (11 + (9 − 1)) + 5 | |
| 11 | (9 + 5) + (11 − 1) | |
| 12 | (11 + 9) + (5 − 1) | |
| 13 | (11 + (5 − 1)) + 9 | |
| 14 | (9 + (5 − 1)) + 11 | |
| 15 | (11 + 5) + (9 − 1) | |