Introduction to Equations

Expression vs. EquationRound 1

• Equation is derived from the word equate, which

means one thing is the same as another thing.

• Which symbol would you associate with equate?

• An = sign!

• In Math, an equation always has an = sign.

• Notice the word equation has part of the word

equal. So when you see equation, you know

you must have an equal sign.

Equation Examples

• Notice they all have an = sign.

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Expression vs. EquationRound 2

• Expression is derived from the word

express, which means high speed or quick.

• An expression does not have an = sign.

• Notice the word expression has the word

express. This is a reminder we want to

write the expression as quickly as possible,

which means no =.

Expression Examples

• Notice no = sign.

Expression vs. EquationRound 3

• What is the relationship between an

equation and an expression?

• Such as 3x - 5 = 8

and 23a + 5b

• Notice each side of the equation is actually an

expression.

• An equation is made from 2 equal

expressions.

How to build an equation...

• Start with 2

expressions

• Put one expression on

the left side of the =

• And the other on the

right side

• Now we have an

equation.

Identify as an Equation or Expression

• An equation is like a balance. The 2 side

are always equal.

Write an equation to represent ...

Each piece of candy costs $.55. The price of p

pieces of candy is $4.40.

• What are we equating?

• The total cost to the cost of the p pieces.

• The amount charged for the candy is found

by multiplying the cost by how many

bought.

• Write the equation

• 4.40 = .55p

Write an equation to represent ...

James made a withdrawal of d dollars from his

checking account. His old balance was $980.23, and

his new balance is $526.87.

• What does withdrawal mean?

• Withdrawal indicates something being taken

away.

• What are we equating?

• Old balance minus withdrawal = New balance

• 980.23 − d = 526.87

Mya organized a pancake breakfast to raise

money to donate to the Habitat for Humanity.

She spent $35.23 on supplies and plans to

charge $4.25 for each breakfast. If P is the

profit and n is number of breakfast’s sold, what is the equation

Mya

can use to determine her profit based on the number of

breakfasts sold?

•What is being equated?

• The profit to the amount spent on supplies and amount

charged.

•How do you show spent mathematically?

• Spent indicates subtraction.

•Write the equation

• P = 4.25n − 35.23

Aiden’s parent’s deposited $1250 into a savings account for

him when he was born and contributed $325 each year, y.

Write the equation that represents the total amount, T.

•What is being equated?

• The amounts put into the account and the total amount.

•What operation does deposited and contributed indicate?

• Addition

•Write the equation

• T = 1250 + 325y

You try...

You try...Tyler receives $15 a week for school lunch, and

the cafeteria charges $2.35 for a lunch.  If Tyler

purchases a lunch daily, write an equation to

determine the amount of money left, A, after d

days.

• What are we equating?

• Amount left = money received minus amount

spent on lunch

• A = 15 − 2.35d

• An equation has an = sign, an expression

does not.

• When writing equations, determine what

2 things are being equated.

• Look for key words to determine the

operation to use.

Key Points to Remember