Writing Algebraic Expressions : Writing Algebraic Expressions Lesson 2-3
Word phrases can be written as 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 : Adding Phrases Plus
More than
Sum
Increased by
Subtracting Phrases : Subtracting Phrases Minus
Difference
Subtracted from
Decreased by
Less than
Multiplying Phrases : Multiplying Phrases Times
Product of Dividing Phrases Quotient
Divided by
Example: 7 decreased by b : Example: 7 decreased by b “Decreased by” means subtract. 7 - b
Example: The product of 19 and k : 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 : 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 : 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 : 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 : 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? : If Steve is 22 years old, then how old is Jerry? s - 4 22 - 4 18 Jerry is 18 years old.
Homework Time : Homework Time