Quick tip guide
| Bill | 15% | 18% | 20% |
|---|---|---|---|
| $25 | $3.75 | $4.50 | $5.00 |
| $50 | $7.50 | $9.00 | $10.00 |
| $75 | $11.25 | $13.50 | $15.00 |
| $100 | $15.00 | $18.00 | $20.00 |
| $150 | $22.50 | $27.00 | $30.00 |
A quick mental trick for 20%: move the decimal one place left to get 10%, then double it. For $64, 10% is $6.40, so 20% is $12.80.