Finding a percent of a numberTextbook 449-493

January 13th 14th, 15th, 16th

Objective

• I can find the percent of a quantity.• I can solve problems involving finding the

whole, if given the part of the whole and percent

Review Vocabulary

• Is means• Equal =• Of means to • multiply.• Equations are going to be very important in

this lesson.• Reminder, in order to solve equations you

have to do the opposite.

New Vocabulary

• Interest: is the amount paid to use money.• Principal; the amount of money you borrow or

save.• Annual interest rate: the amount of money

you earn or pay per year

Finding the percent of a Number

• There are three ways to find the percent of a number.

• Change the percent to a decimal then multiply.• Change the percent to a fraction then multiply.• By making a proportion.• Lets see what you find easier.• 50% of 8 • What way did you use?

Try some more!

• Find 25% of 48• 12, explain how you found your answer• 10% of 85• 8.5• 45% 0f 20• 9• 60% of 60• 36

Find the whole number given the part and percent

• 25% of what number is 8• Rewrite as an equation. • .25 x n = 8• How do I solve?• Divide both sides by .25• The answer is 32

Try some!

• 20% of what number is 30• 150• 40% of what number is 60• 150• 75% of what number is 54• 72

Finding a discount

• What is a discount? Give me an example• The discount is the amount that you will get off

of the regular price.• Find the discount, (by finding the percent of the

number) usually a percent off.• Then subtract from the original price, the answer

you get is the sale price.

Example

• A pair of pants cost $36. The sale price is 25% off the regular price. What is the sale price?

• 25% of $36• What are we going to change 25% to.• 0.25 x $36 • $9• Then subtract from the original price.• $36-$9 • $27 is he sale price of the pants

Try some

• A regular price for a shirt is $40. • Find the sale price if the discount is 15%.• $34• Find the sale price if the discount is 40%• $24

Is there another way!

• Can anyone think of another way to do these types of problem.

• If you know that you will not have to pay the discount part, you will pay whatever percent is left.

• If there is a 30% discount, that means you will pay 70% of the amount. This eliminates one step.

Finding Sales Tax

• Sales Tax is something extra you have to pay besides the price of something.

• Anyone know what the sales tax is in Lorain county?

• Find the sales tax the same way you find the percent of a number, then add that to the original number.

Example• You are buying cat food for $9. The sales tax is

6%. What is the total of the purchase?• 6% x 9• 0.06 x 9• .54 cents• $9.00 + .54 = $9.54

Try One!

• Cat toy is $8.00. The sales Tax is 6%. What is the cost.

• $8.48• You are buying a pair of shoes that cost

$28.80. There is a 5% sales tax. What is the total amount of your purchase.

• $30.24

Tips

• A tip is added to the total of a bill. It is found the same way that you find the percent of a number.

• Standard tipping amount is what?

Simple Interest

• Interest paid on only the principal.

• Formula• SI=Principal x annual interest Rate x Time in years