题干
计算：
+
+
+
+
+
+
+
+
=____
| 1 |
| 1 |
| × |
| 2 |
| 1 |
| 2 |
| × |
| 3 |
| 1 |
| 3 |
| × |
| 4 |
| 1 |
| 4 |
| × |
| 5 |
| 1 |
| 5 |
| × |
| 6 |
| 1 |
| 6 |
| × |
| 7 |
| 1 |
| 7 |
| × |
| 8 |
| 1 |
| 8 |
| × |
| 9 |
| 1 |
| 9 |
| × |
答案(点此获取答案解析）
| 9 |
