Percentages are ratios of an amount compared to 100. The percent change of an old to new value is equal to 100% x \({ new - old \over old }\).
Betty scored 90% on her final exam. If each question was worth 3 points and there were 90 possible points on the exam, how many questions did Betty answer correctly?
| 28 | |
| 27 | |
| 15 | |
| 39 |