Percentages are ratios of an amount compared to 100. The percent change of an old to new value is equal to 100% x \({ new - old \over old }\).
Roger loaned Bob $500 at an annual interest rate of 4%. If no payments are made, what is the interest owed on this loan at the end of the first year?
| $20 | |
| $72 | |
| $36 | |
| $18 |