This document discusses variables, expressions, and formulas. It defines key terms like variable, value, and variable expression. It provides examples of variable expressions and how to evaluate them by replacing variables with values. Real-life examples are given like calculating average speed from a travel time and distance. Geometric formulas are also presented, such as the area of a triangle formula, and examples are worked through of evaluating geometric expressions.

1. VARIABLES, EXPRESSIONS AND
FORMULAS

2. VOCABULARY
 Variable – a letter used to represent one or more
numbers
 Values – numbers
 Variable expression – a collection of numbers,
variables, and operations
 Evaluate the expression – replace each
variable in an expression by a number

3. DESCRIBING THE VARIABLE EXPRESSION

4. EXAMPLES OF VARIABLE EXPRESSIONS
(What does each expression ask you to do?)

5. EVALUATE

6. EVALUATE REAL-LIFE EXPRESSIONS
 Find the average speed (in miles per hour) of a car that
traveled 180 miles from Hartford, Connecticut to
Matawan, New Jersey in 3 hours.
Rate of speed (r) = Distance (d)/Time (t)
Rate = 180 miles/3 hours = 60 miles per hour (mph)
 You hike on a trail at 2 miles per hour. How long will it
take you to hike if the round-trip distance is 7.4 miles?
Time (t) = Distance (d)/Rate (r)
Time = 7.4 miles/2 miles per hour = 3.7 hours

7. EVALUATE A GEOMETRIC EXPRESSION
2
or
2
1 bh
AbhA 
Example
Find the area of a triangle with a base of 10 inches and a
height of 6 inches.

8. EVALUATE A GEOMETRIC EXPRESSION
P = a + b + c
Example
Find the perimeter of a triangle with side lengths 3 inches, 9
inches, and 11 inches.