Transcript 1_1 Variables and Expressions

1.1 Variable and Expressions:
Quantity: Anything that can be measured
or counted.
Variable: A symbol, usually a letter, used
to represent the value of a variable
quantity.
Algebraic Expression: A mathematical
phrase that includes one or more
variables.
Numerical Expression: A mathematical
phrase involving numbers and operation
symbols, but not variables.
GOAL:
REAL-WORLD:
A student writes the word phrase
“the quotient of n and 5” to describe
the expression 5/n. Describe and
correct the student’s error.
SOLUTION:
Using the definition of quotient = fraction, we
see that :
5/n  the quotient of 5 and n.
n/5  the quotient of n and 5.
Thus the student has the two
variables backwards.
YOU TRY IT:
Write an algebraic expression for
the following sentence:
“8 minus the product of 9 and r”
SOLUTION:
Using the basics we learned in Pre-Algebra we
know that :
Minus  subtraction
Product  multiplication
8 minus  8 Product of 9 and r  9r
Therefore: 8 – 9r is the expression.
YOU TRY IT:
Write an algebraic expression for
the following sentence:
“3 less than 2 times a number”
SOLUTION:
Using the basics we learned in Pre-Algebra we
know that :
3 Less than  subtraction placed at
the end of the sentence  - 3
2 times  multiplication  2( ), 2∙, 2×
A number  n to represent any
number
Therefore: 2n- 3 is the expression.
VIDEOS:
Variables
and Expressions
Variables:
http://www.khanacademy.org/math/algebra/intro
duction-to-algebra/variable-andexpressions/v/what-is-a-variable
Expressions:
http://www.khanacademy.org/math/algebra/intro
duction-to-algebra/variable-andexpressions/v/variables-and-expressions-1
CLASSWORK:
Page 20-22:
Problems: 1, 3, 5,
6, 7, 10, 24
33, 37, 46, 56.