VARIABLES IN ALGEBRA

Lesson 1.1

Objective/ Essential Question

Objective: By the end of this lesson, you will be able to answer the question: How do you evaluate a variable expression?

Key Vocabulary Words

Variable: a letter that is used to represent one or more numbers

Values: the numbers the variable represents

Variable Expression: a collection of numbers, variables, and operations

Evaluating the expression: replacing each variable by a number

Example One

Evaluate the expression when y=2

A. 8y

B. 10

y

C. y+3

D. 14-y

Example 2

Average Speed= (d t)

Find the average speed (in miles per hour) of a car that traveled 180 miles from Boise, Idaho, to Minidoka National Refuge in 3 hours

Example 3

The perimeter of a triangle is equal to the sum of the lengths of its sides:

Find the perimeter of a triangle with the dimensions: a=8 feet, b=15 feet, c=17 feet

Example 4

The simple interest earned by money P (called the principal) at an annual interest rate r and t years is given by Prt.

You deposit $650 at a rate of 8% per year. How much simple interest will you earn after one half of a year?

Example 5

You plan to go hiking in the Jedediah Smith Redwoods State Park in California. You estimate you’ll hike at a rate of 2 miles per hour on a steep trail. How low will it take you to hike from Howland Hill Road along the Boy Scout Tree Trail and back?