July 03, 2012
1.1 Expressions and Variables
Learning outcome
To evaluate and write variable expressions
Variable
A letter used to represent one or more numbers
Numerical Expression
An expression that consists of numbers and operations
Variable Expression
An expression that consists of numbers, variables and operations
July 03, 2012
Evaluating an expression
Solving the problem by substituting a # for the variable,
solving the problem or just simplifying the an answer
Evaluate the expressions
3 · 2b when b = 9
2x + 3y - 2x when x = 3 and y = 4
2x + 5y - x when x = 4 and y = 8
y
July 03, 2012
Verbal Model
Describes a problem using words and uses math symbols to relate
the words
Common Words and Phrases that Indicate Operations
Addition
Subtraction
Multiplication
Division
plus
minus
times
divided by
the sum of
the difference of the product of
increased by decreased by
multiplied by
total
fewer than
of
more than
less than
added to
subtracted from
divided into
the quotient of
A number added to 27
The product of a number and 7
29 decreased by a number
The quotient of 56 and a number
July 03, 2012
You have a 350-page manuscript that needs to be edited
very quickly. You are going to divide the number of pages
among several editors. You want to give the same number
of pages to each editor. Write a variable expression fthat
describes the situation
Number of pages
for each editor
Total number
of pages
=
÷
Number of
editors
You belong to a book club. Your yearly book budget is $350.
Each book in the book club costs $7.
Books
Cost ($)
Amount left ($)
1
7
343
2
14
336
3
4
Write a variable expression for the cost of b books.
Write a variable expression for the amount of your budget after b
books.
How many books will you be able to buy before the $350 is spent?