Percentages
Work with percents and percent problems
lessons (8)
Introduction to Percentages
Learn what percentages are and how they relate to fractions and decimals.
Finding Percent of a Number
Learn how to calculate any percentage of a number using multiplication and conversion techniques.
Percent Increase and Decrease
Learn how to calculate percent increase and percent decrease to measure changes in quantities.
Percent Proportion
Use the proportion part/whole = percent/100 to find a missing part, whole or percent with cross multiplication.
Percent Equation
Solve any percent problem with one equation: part = rate × whole. Find the part, the whole or the percent, even above 100% and below 1%.
Markup and Markdown
Learn how stores set prices with a markup on the cost price and lower them with a markdown, and how to find the percent, the original price and the result of stacked discounts.
Commission
Learn how salespeople earn commission: find the commission, total earnings with a base salary, the commission rate, the sales needed for a target income and tiered commission.
Percent Error
Learn how to measure how far a measurement or estimate is from the actual value, as a percent of the actual value.
Percentages express numbers as parts of 100, making comparisons intuitive and standardized. When a store offers 25% off, you instantly understand you save one quarter of the price. When statistics report that 68% of people prefer option A, you can easily compare this to other percentages. This universal language of proportion appears everywhere from nutrition labels to election polls.
Understanding percentages involves three key calculations: finding a percentage of a number (what is 15% of 80?), finding what percentage one number is of another (12 is what percent of 48?), and finding the whole when given a part and percentage (30 is 20% of what number?). Mastering these unlocks real-world applications in shopping, finance, and data analysis.
What Students Will Learn
- Calculate a percentage of any number
- Find what percent one number is of another
- Determine the whole given a part and its percentage
- Calculate percentage increase and decrease
- Apply percentages to discounts, taxes, and tips
Frequently Asked Questions
What is the easiest way to calculate 10% of something?
Simply move the decimal point one place to the left. 10% of 250 is 25. From there, you can easily find 5% (half of 10%), 20% (double 10%), or combine to find others.
How do I calculate percentage change?
Use the formula: ((New - Original) / Original) × 100. If a price goes from 80 dollars to 100 dollars, the increase is ((100-80)/80) × 100 = 25%.
Why do stores say 50% off feels like a better deal than half off?
They are identical! Psychologically, larger numbers can feel like bigger deals. 50% sounds like more than 1/2, even though they represent the same discount.