Using Proportions to Solve Percent

ProblemsMCC7.RP.3: Use proportional relationships

to solve multistep ratio and percent problems.

Examples: simple interest, tax, markups and markdowns, gratuities and

commissions, fees, percent increase and decrease, percent error.

What are they??What do you know about these

examples?

• simple interest, • tax, • markups and markdowns, • gratuities and commissions, • fees, • percent increase and decrease, • percent error.

Use this proportion to solve percent

problems:

Using Proportions to Solve Percent Problems

The original price of a cell phone is $99.50. Sales tax is 7%. What is the selling price of the cell phone?

Percent Part 7% x100 Whole 100 99.50

Using Proportions to Solve Percent Problems

**Cross multiply to solve**

7% x 100 99.50

(7) (99.50) = 100x696.50 = 100x *divide by 100

6.97 = x *tax is $6.97. Add to original price of cell phone.

99.50 + 6.97 = 106.47

Selling price of cell phone is $106.47

Using Proportions to Solve Percent Problems

• You try one!

• A shirt that is originally $24.95 is on sale for a discount of 20%. What is the selling price of the shirt before tax?

Using Proportions to Solve Percent Problems

• Tax is 6%. What is the total cost to purchase the shirt?