Expressions and Variables (1 Expressions and Variables (1.1)
Numerical Expression: consist of numbers and operations
Example: 410,
3 + 5, 7-2…
 What are two other ways 410 can be written?
Variable: a letter used to represent one or more numbers.
Variable Expression: consist of numbers, variables, and operations.
 Write three examples of a variable expression.
Evaluate: to evaluate a variable expression, substitute a number
for each variable and evaluate the resulting numerical expression.
Example: Evaluate the expression 5b when b=10.
5b
510
50
 Evaluate the expression when x=6 and y = 12.
1. y + 8
2. 9 – x
3. y – x
4. xy
Writing Variable Expressions
You can solve a real-world problem by creating a verbal model and using it to
write a variable expression. A verbal model describes a problem using words
as labels and using math symbols to relate the words. The table shows
common words and phrases that indicate mathematical operations.
Common Words and Phrases that Indicate Operations
Subtraction
Multiplication
Division
plus
the sum of
increased by
total
more than