| 118320 | ( | m | − | 1 | ) | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) | = | 780000 | m |
| Left side of the equation = | 118320 | m | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) | − | 118320 | × | 1 | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) |
| = | 118320 | m | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) | − | 118320 | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) |
| = | 118320 | m | × | 1 | + | 118320 | m | × | 2 | + | 118320 | m | × | 3 | + | 118320 | m | × | 4 |
| = | 118320 | m | + | 236640 | m | + | 354960 | m | + | 473280 | m | + | 118320 | m | m | − | 118320 |
| = | 1183200 | m | + | 118320 | m | m | − | 118320 | ( | 1 | + | 2 | + | 3 | + | 4 | + | m | ) |
| = | 1183200 | m | + | 118320 | m | m | − | 118320 | × | 1 | − | 118320 | × | 2 | − | 118320 | × | 3 | − | 118320 |
| = | 1183200 | m | + | 118320 | m | m | − | 118320 | − | 236640 | − | 354960 | − | 473280 | − | 118320 | m |
| = | 1064880 | m | + | 118320 | m | m | − | 1183200 |
| 1064880 | m | + | 118320 | m | m | − | 1183200 | = | 780000 | m |