Lesson 10
What Are Percentages?
Let’s learn about percentages.
10.1: Dollars and Cents
Find each answer mentally.
 A sticker costs 25 cents. How many dollars is that?
 A pen costs 1.50 dollars. How many cents is that?
 How many cents are in one dollar?
 How many dollars are in one cent?
10.2: Coins

Complete the table to show the values of these U.S. coins.
coin penny nickel dime quarter half dollar dollar value (cents) The value of a quarter is 25% of the value of a dollar because there are 25 cents for every 100 cents.

Write the name of the coin that matches each expression.
 25% of a dollar
 5% of a dollar
 1% of a dollar
 100% of a dollar
 10% of a dollar
 50% of a dollar
 The value of 6 dimes is what percent of the value of a dollar?
 The value of 6 quarters is what percent of the value of a dollar?
Find two different sets of coins that each make 120% of a dollar, where no type of coin is in both sets.
10.3: Coins on a Number Line
A $1 coin is worth 100% of the value of a dollar. Here is a double number line that shows this.
 The coins in Jada’s pocket are worth 75% of a dollar. How much are they worth (in dollars)?
 The coins in Diego’s pocket are worth 150% of a dollar. How much are they worth (in dollars)?
 Elena has 3 quarters and 5 dimes. What percentage of a dollar does she have?
Summary
A percentage is a rate per 100.
We can find percentages of \$10 using a double number line where 10 and 100% are aligned, as shown here:
Looking at the double number line, we can see that \$5.00 is 50% of \$10.00 and that \$12.50 is 125% of \$10.00.
Glossary Entries
 percent
The word percent means “for each 100.” The symbol for percent is %.
For example, a quarter is worth 25 cents, and a dollar is worth 100 cents. We can say that a quarter is worth 25% of a dollar.
 percentage
A percentage is a rate per 100.
For example, a fish tank can hold 36 liters. Right now there is 27 liters of water in the tank. The percentage of the tank that is full is 75%.