| 100 | ( | a | ÷ | 2 | + | 1 | ) | × | 500 | ( | a | + | 1 | ) | = | 660000 |
| 方程左边 = | 50000 | ( | a | ÷ | 2 | + | 1 | ) | ( | a | + | 1 | ) |
| 50000 | ( | a | ÷ | 2 | + | 1 | ) | ( | a | + | 1 | ) | = | 660000 |
| 方程左边 = | 50000 | a | ÷ | 2 | × | ( | a | + | 1 | ) | + | 50000 | × | 1 | ( | a | + | 1 | ) |
| = | 25000 | a | ( | a | + | 1 | ) | + | 50000 | ( | a | + | 1 | ) |
| = | 25000 | a | a | + | 25000 | a | × | 1 | + | 50000 | ( | a | + | 1 | ) |
| = | 25000 | a | a | + | 25000 | a | + | 50000 | ( | a | + | 1 | ) |
| = | 25000 | a | a | + | 25000 | a | + | 50000 | a | + | 50000 | × | 1 |
| = | 25000 | a | a | + | 25000 | a | + | 50000 | a | + | 50000 |
| = | 25000 | a | a | + | 75000 | a | + | 50000 |
| 25000 | a | a | + | 75000 | a | + | 50000 | = | 660000 |