SAT Percentages Questions
Percent of, percent change, and working backwards from a result to the original amount.
In short
- Percentages is part of Problem-Solving and Data Analysis, about 15% of the scored Math questions: 5 to 7 on every test.
- Math questions from all four areas are mixed in each module and arranged from easiest to hardest.
- Percent-change base is the trap Rivie's practice tests set most often in Percentages questions.
Common traps
Most common first, from Rivie's ten practice tests.
Percent-change base
Percent-change problems require dividing by the original value; the wrong choice divides by the new value or by the difference.
The usual mistake: You compute |new − old| correctly and then divide by 'whichever feels like the base,' without locking in 'change is always relative to the original.'
Compound percent (not additive)
Two successive percent changes don't add: a 20% increase followed by a 20% decrease is not 0%. The wrong choice adds them.
The usual mistake: You apply percentages to the original each time instead of compounding (multiplying 1.20 × 0.80 ≠ 1.00).
Try a question
From Rivie's practice tests. Pick an answer to see why it is right or wrong.
A town's population grew from 2,500 to 3,200 over five years. By what percent did the population grow?
Video lessons
Free on YouTube, picked for this topic.