1. Variables in Algebra Goals I can evaluate a variable expression.
I can write variable expressions for word phrases.
I can write a variable expression that models a real life situation.

2. Variables and Expressions
Special Vocabulary: variable, constant, numerical expression, algebraic expression
Variable- a letter or symbol that can be used for a value that can change.
Constant – a value that does not change.
Numerical expression – a mathematical phrase that contains only constants and/or operations
Algebraic expression – a mathematical phrase that may contain variables, constants, and/or operations

3. Variables and Expressions
We can replace the variables with numbers and evaluate the expression.
To evaluate an expression is to find it’s value. We evaluate when we simplify to the lowest possible value after substituting the number for the variable.

4. Evaluate the Expression when y = 3
YOU TRY:
Evaluate the Expression when y = 3
a. 4y b.
c. y + 8
d y

5. We have to be able to “translate” words into expressions
What words indicate a particular operation?
Add Subtract
Sum
Plus
More than
Increase(d) by
Perimeter
Deposit
Gain
Greater than
Up (flights of stairs)
Total
Minus
Take away
Difference
Reduce(d) by
Decrease(d) by
Withdrawal
Less than
Fewer (than)
Loss of

6. We have to be able to “translate” words into expressions
What words indicate a particular operation?
Multiply Divide
Split into __ parts
Cost each
Quotient
One-half (÷2), Third (÷3), Quarter (÷4)
Into
Per
Percent (out of 100)
Times
Product Of
Twice (×2), double (×2), triple (×3), etc.
Half (×½), Third (×⅓), Quarter (×¼)
Area (by)
Percent (of)
Square (times itself 2 times)
Cube (times itself 3 times)
… to the power of ___
(times itself ___ times)

7. Variables and Expressions
Let’s try an example of “translating” a phrase into an algebraic expression:
Nine more than a number y
Can you identify the operation?
“more than” means add
Answer: y + 9

8. Variables and Expressions
Let’s try another example of “translating” a phrase into an algebraic expression:
4 less than a number n
Can you identify the operation?
“less than” means Subtract
Answer: n – 4.
Why not 4 – n?????
**Expressions that contain subtracting will be the hardest for us!

9. Variables and Expressions
Let’s try another example of “translating” a phrase into an algebraic expression:
A number a divided by 12
Can you identify the operation?

10. Variables and Expressions
This one is harder……
5 times the quantity 4 plus a number c
Can you identify the operation(s)? What does the word quantity mean? Hmm……

11. HOMEWORK
Pg EVENS