| 100 | ÷ | ( | 1 | + | r | ) | × | 1 | + | 100 | ÷ | ( | 1 | + | r | ) | × | 2 | + | 75 | ÷ | ( | 1 | + | r | ) | × | 3 | + | 75 | ÷ | ( | 1 | + | r | ) | × | 4 | = | 0 |
| Multiply both sides of the equation by: | ( | 1 | + | r | ) |
| 100 | × | 1 | + | 100 | × | 2 | + | 75 | × | 3 | + | 75 | × | 4 | + | 50 | × | 5 | + | 25 | × | 6 | = | 0 |
| 100 | × | 1 | + | 100 | × | 2 | + | 75 | × | 3 | + | 75 | × | 4 | + | 50 | × | 5 | + | 25 | × | 6 | = | 0 |
| 100 | + | 200 | + | 225 | + | 300 | + | 250 | + | 150 | − | 250 | − | 250 | r | = | 0 |
| 975 | − | 250 | r | = | 0 |
| - | 250 | r | = | 0 | − | 975 |
| - | 250 | r | = | - | 975 |
| 975 | = | 250 | r |
| 250 | r | = | 975 |
| r | = | 975 | ÷ | 250 |
| = | 975 | × | 1 250 |
| = | 39 | × | 1 10 |
| r | = | 39 10 |
| r | = | 3.9 |