Writing Algebraic Expressions

Word phrases can be written as algebraic expressions. Use the words to determine what operation you are using. Use a variable for the phrase “ a number. ”

Adding Phrases Plus More than Sum Increased by

Subtracting Phrases Minus Difference Subtracted from Decreased by Less than

Multiplying Phrases Times Product of Dividing Phrases Quotient Divided by

Example: 7 decreased by b “Decreased by” means subtract. 7 - b

Example: The product of 19 and k “Product” means multiply. We show multiplication by placing the factor right next to the variable. 19k

Less than, more than Some word phrases contain the words “ less than ” or “ more than. ” When you see those words, start with the second part of the phrase. Example: 23 less than m m - 23

Example: 32 less than 5 times c The 32 is less than the 5 times c, which means we subtract 32 from the 5 times c. So, start with 5 times c. 5c - 32

Describing Unknown Numbers When you don ’ t know what a number is, let a variable stand for that number. Use an algebraic expression to describe what you ’ re looking for.

Example Write an algebraic expression to describe Jerry’s age. Use the following information: Jerry is 4 years younger than his brother Steve. First, we have to know how old Steve is. We do not have an age for Steve, so we will use a variable: Let s = Steve’s age. Now that we have determined Steve’s age (s), we can use it to determine Jerry’s age. Jerry is 4 years younger than Steve. s - 4

If Steve is 22 years old, then how old is Jerry? s Jerry is 18 years old.