Percents A Percent is a ratio that compares a number to 100. The symbol for percent is %.

You can write percents as fractions and decimals.

36% as a decimal would be .36

As a fraction it would be 36/100 = 9/25

Percent of a Whole Number Using Proportions

Formula:

is = %

of 100

“Is over of equals

percent over 100!”

Practice:

1)18% of 40

2)25% of 50

3)75% of 480

4)43% of 61

Practice:

5) 500 is 45% of what number?

6) What number is 50% of 140?

7) 43.2 is what percent of 72?

8) 100 is what percent of 500?

Percent of Increase and Decrease*When a beginning and ending amount are given

and you are asked to find the percent of increase or decrease from the beginning amount to the ending amount, you need to use the formula shown below:

Amount of increase or decrease (change) = %

original amount 100

So, we must first find the difference between the beginning and ending amount (amount of increase or decrease)

Then, you set up the proportion, cross multiply and solve for the %!

Practice:

1)The enrollment at a university increased from 14,000 students to 16,000 students over a period of 5 years. What is the percent increase in enrollment?

2) The selling price of a home was dropped from $200,000 to $190,000. By what percent did the price drop?

3) My real estate agent told me that my house had appreciated in value over the last three years. In other words, it has gone from being worth $102,500 to being worth $111,000. What is the percent increase in the value of my house?

A. 8.29% B. 2.76% C. 7.66%

Discount• Discount is good for the consumer. It

SAVES you money!

How to find Discount and Sale Price:• 1) change the % off to a decimal (move

2 places to the left PDL)• 2) Multiply the original price by the %

discount = DISCOUNT AMOUNT• 3) Subtract the savings from the original

price = SALE PRICE

Practice

• You find a pair of jeans you want for 25% off the original price of $75.00.

• Step 1: Change 25% to .25• Step 2: Multiply .25 by 75 =

_________ (discount)• Step 3: Subtract the discount from

the original price = SALE PRICE

Original Price

• How to find the original price: Formula: discount amount = % original price 100

Practice• You and your family want to buy a

printer. The printer is marked down 35%. Because of this sale, you will save $30.75. What is the original price of the printer?

Sales Tax• The sales tax rate is given as a % (i.e.

the sales tax in Auburn in 8%) Tax is ADDED on to your total!

How to find the Sales Tax and Final Price:1) Change the % to a decimal (PDL)2) Multiply the decimal by the subtotal =

TAX AMOUNT3) Add the tax amount to your subtotal

(original price) = FINAL PRICE

Tax Formula

•Original x % tax = Tax Amount

Practice

• You went to Olive Garden in Auburn (8% tax rate). Your bill was $45.00. What is the final price?

Tip• Tip is ADDED on to your bill. • People normally tip 10%, 15%, or

20%How to find Tip and Total:1) Determine the percent that you

are going to tip2) Change the % to a decimal (PDL)3) Multiply the decimal by the total

bill = TIP4) ADD the Tip onto the bill =

GRAND TOTAL

Tip Formula:

•$ Total x 0.15 = tip

Practice1) Mr. Clark wants to leave a 12% tip.

How much tip should he leave if his family’s bill is $28.45?

2) Jose’s bill at Chili’s cost $18.56. The tax rate is 8% and he wants to tip the waiter 15%. What is the final bill going to be?

Commission • Commission is the percent of a sale that

a sales person makes• percentage of the total cost.

Example: Jack's Gallery sold Amanda's painting for $500, so Amanda paid them 10% commission.

• Formula: $Total x % Commission = commission

Practice1) A salesperson makes a 15%

commission on all sales. How much does the salesperson make on a $45,000 sale?

2) A used car salesperson makes a commission of 20%. How much would the salesperson make on a sale of $11,000?

Simple Interest

Formula: I = PRT Interest = Principal (origin) x Rate x Time

*This formula figures out the cost of borrowing money OR the amount you earn when you put money in a savings account. Interest can HELP or HURT you.

Annual = Yearly

• I = Interest = The amount charged by the bank other lender

• P= Principal = the amount you borrow

• R= Rate = The interest rate the bank is charging you

• T = Time = How many years you will take to pay off the loan

1) You want to buy a used truck, so you go to the bank to borrow $7,000. The bank will charge you interest on the $7,000. If the simple interest rate is 9% for four years, what will be the cost of interest?

Practice

2)Sarah puts $300 into a savings account with 5% simple annual interest. She makes no more deposits or withdrawals.

• How much is in her account after one year?

• How much is in her account after two years?