Percents
A free Pre-Algebra lesson from the “Number Foundations” unit, with a worked example and practice problems including step-by-step solutions.
Percent means per 100. To convert a percent to a decimal, divide by 100. To find a percent of a number, multiply the decimal form of the percent by the number. In Number Foundations, the goal is not just to get an answer but to recognize the structure of the problem, choose a reliable strategy, and explain why the result is reasonable. The practice set now includes targeted skill work, transfer questions, and mixed review so students build fluency and retention.
What you'll learn
- Convert between percents, decimals, and fractions
- Find percent of a number
- Solve discount and increase problems
Worked example
Problem. Find 15% of 80.
- Convert 15% to 0.15.
- Multiply 0.15 by 80.
- 0.15 x 80 = 12.
- Connect the calculation back to Percents so the method, not just the arithmetic, is clear.
Answer: 12
Lesson preview: this page shows 5 practice items. The interactive activity contains 28 practice items and 15 quiz items (typed response and multiple choice). Counts include repeated prompts and variants.
Practice problems
1. Write 25% as a decimal.
Show solution
- Divide 25 by 100.
- 25% = 0.25.
Answer: 0.25
2. Write 0.4 as a percent.
Show solution
- Multiply 0.4 by 100.
- 0.4 = 40%.
Answer: 40
3. Which fraction equals 50%?
Choices: 1/2 · 1/4 · 3/4 · 1/5
Show solution
- 50% means 50 out of 100.
- 50/100 simplifies to 1/2.
Answer: 1/2
4. Find 10% of 90.
Show solution
- 10% is 0.10.
- 0.10 x 90 = 9.
Answer: 9
5. Find 20% of 45.
Show solution
- 20% is 0.20.
- 0.20 x 45 = 9.
Answer: 9
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