Percentages • Topic 1 of 8

Percentage Concepts

A percentage is a fraction out of 100: P% means P/100. To find P% of a number, multiply by P/100 (or move the decimal two places and multiply). To express one quantity as a percent of another, divide part by whole and multiply by 100. To recover the whole from a part and its percentage, divide the part by P/100. Converting fluently between percent, fraction and decimal — 25% = 1/4 = 0.25 — is the single most useful skill here, and the SAT rewards doing these conversions in your head or quickly on the calculator.

✅ Solved examples

1. What is 20% of 150?
20% = 0.20, so 0.20 × 150 = 30.
2. 12 is what percent of 48?
12 ÷ 48 = 0.25 = 25%.
3. 30 is 25% of what number?
Whole = 30 ÷ 0.25 = 120.
4. Write 3/5 as a percent.
3 ÷ 5 = 0.6 = 60%.

✏️ Practice — try these, take hints as needed

1. What is 15% of 200?
15% = 0.15.
Multiply by 200.
Compute.
30.
2. 9 is what percent of 36?
Divide part by whole.
9 ÷ 36 = 0.25.
Multiply by 100.
25%.
3. 48 is 40% of what number?
Whole = part ÷ (P/100).
48 ÷ 0.40.
Compute.
120.
4. Write 7/20 as a percent.
Divide 7 by 20.
0.35.
× 100.
35%.
5. What is 8% of 250?
8% = 0.08.
0.08 × 250.
Compute.
20.

📝 Topic test — 8 questions

Auto-graded with full solutions; saved to your dashboard. Use the calculator and formula sheet (top-right) any time.

Loading questions…
Percentage Increase →