Unit 10: Percentages
A percent as literally out of 100, turned into discounts, tips, and how much something grew or shrank.
7 topics · 28 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
What a Percent Actually Means
- How it worksHow does shading in 27 out of 100 little squares on a grid show what 27 percent looks like?
- How it worksHow does putting a mark on a number line from 0 to 100 show what 62 percent means?
- Worked exampleFind what percent is shaded if 38 out of 100 squares in a grid are colored in.
- Common mistakeWhy isn't 50 percent of a giant pizza the same amount as 50 percent of one small cookie?
Your turn1 of 2
An art project uses a 100-square grid, and Nina colors in 69 of the squares. What percent of the grid is colored?Converting Between Percents, Decimals, and Fractions
- How it worksHow do you turn a decimal like 0.75 into a percent by moving the decimal point two spots?
- Worked exampleFind the percent and decimal that match the fraction 3 fourths of a candy bar eaten.
- Ties togetherHow does turning 3 fourths into 75 percent connect to finding equivalent fractions like 3 fourths and 6 eighths?
Your turn1 of 2
Leo answered 3 over 8 of his quiz questions correctly. What percent of the quiz did he get right?Finding a Percent of a Number
- How it worksHow do you find 30 percent of a number by turning it into the decimal 0.3 and multiplying?
- Common mistakeWhy can you find 15 percent of 40 candies even though 40 isn't 100?
- Common mistakeWhy doesn't finding a percent of a number always make the number smaller?
- Worked exampleFind how many stickers 40 percent of 25 stickers actually is.
- Going furtherWhat happens to your answer if you find 40 percent of 50 stickers instead of 25 stickers?
Your turn1 of 2
Priya has 68 stickers in her collection, and 64 percent of them are shiny. How many shiny stickers does she have?Finding What Percent One Number Is of Another
- How it worksHow do you find what percent 9 is of 36 by turning it into the fraction 9 over 36 first?
- Worked exampleFind what percent 14 is of 40 kids in a class who play soccer.
- Common mistakeWhy isn't the answer to what percent 8 is of 40 the same as what percent 40 is of 8?
- Going furtherWhat happens to the percent if 8 out of 40 kids becomes 8 out of 20 kids instead?
Your turn1 of 2
Ravi got 21 questions right out of 63 on a test. What percent did he get right?Calculating a Discount
- How it worksHow do you find a 20 percent discount on a toy by first finding 20 percent of the original price?
- Worked exampleFind the sale price of a 40 dollar skateboard that is 25 percent off.
- Common mistakeWhy does a 20 percent off sign always mean 20 percent of the original sticker price, never an already-discounted one?
Your turn1 of 2
A skateboard normally costs 73 dollars and is on sale for 41 percent off. What is the sale price?Calculating a Tip
- How it worksHow do you find a 10 percent tip on a restaurant bill by moving the decimal point one place?
- How it worksHow do you turn a 10 percent tip into a 20 percent tip by doubling what you just found?
- Worked exampleFind a 15 percent tip on a 20 dollar pizza delivery bill.
- Common mistakeWhy doesn't tipping 15 percent mean adding exactly 15 dollars no matter how big the bill is?
- Going furtherWhat happens to the tip amount if the bill grows from 20 dollars to 50 dollars but the percent stays at 15?
Your turn1 of 2
Amara's family's dinner bill comes to 68 dollars, and they want to leave a 20 percent tip. How much is the tip?Percent Increase and Decrease
- How it worksHow do you find a percent increase by comparing how much a number grew to what it started at?
- Common mistakeWhy doesn't a 50 percent increase followed by a 50 percent decrease bring a number back to where it started?
- Worked exampleFind the percent increase when a plant grows from 20 centimeters to 25 centimeters tall.
- Going furtherWhat happens to the percent decrease if a 40 dollar price drops to 30 dollars instead of 20 dollars?
Your turn1 of 2
Zoe's sunflower grows from 31 centimetres to 66 centimetres tall. What is the percent increase in its height?