Transcript Lesson 1.1 Variable Expression

1.1 Variables in Algebra
How 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 represent
the 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_______y
Division
c.
14 , 14÷y
y
9 + a
9________a
Addition
d.
12 – b
12_______b
Subtraction
Example 2: Write a variable expression
a.
b.
c.
d.
Eight more than a number
n + 8
Five less than a number
n –5
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 our
warm-up exercise?
2(n + 5) – 2n – 10
Example 3: Evaluate (solve) the variable expression
When x = 5
Expression
Substitute
Simplify
a.) 5x
b.) 40
x
5•5
25
40
5
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
2
In Class: Pg. 6 #1-4, 6-16
Homework: Pgs. 6-8 #17-27, 34-37, 50-60even
Extra credit: (5 points) #40, 43, 46, 51