1.1 Variables in AlgebraHow many miles has the bike traveled?

A racing biker travels down the road at 35 miles per hour. How many miles will the bike travel in 3 hours?

Objectives: to write and evaluate variable expressions

• Try the warm-up exercise• Definitions:

Variable -a letter that is used to represent a

range of numbers. (ex. n, x, y)

For Example: We can let the letter n representthe number we chose to begin the warm-up exercise.

Variable expression - expressions that consist of variables, constants, and math operations.

Ex. 8y, 4 + x, 16 b

Example 1: Describe the variable expression

Variable expression Meaning Operation

a. 3x, 3 • x, (3)(x) __times__ Multiplication

b. 14 , 14÷y 14_______y Division y

c. 9 + a 9________a Addition

d. 12 – b 12_______b Subtraction

Example 2: Write a variable expressiona. Eight more than a number

n + 8b. Five less than a number

n – 5c. A number divided by 3

n/3 or n ÷ 3• Five more than three times a number

3n + 5

Can you now write a variable expression for ourwarm-up exercise?

2(n + 5) – 2n – 10

Example 3: Evaluate (solve) the variable expressionWhen x = 5

Expression a.) 5x b.) 40 x

Substitute 5 • 5 40 5

Simplify 25 8

Example 4: Evaluate rt to find distance (d = rt)

Find the distance (d) of our biker who rode 3 hours (t time in hours) and went an average speed of 35 miles per hour (r rate).

Solution: d = (35)(3) d = 105 miles

(What if the time changes to 30 minutes?)

Review vocabulary:Perimeter -

the distance around a polygon(note: add together the length of the sides)

Area - the space inside a closed geometric shape(note: use a formula to calculate area)A(triangle) = bh A(rectangle) = lw

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In Class: Pg. 6 #1-4, 6-16Homework: Pgs. 6-8 #17-27, 34-37, 50-60evenExtra credit: (5 points) #40, 43, 46, 51