1. Section 3.9 Percents Mr. Beltz & Mr. Sparks

2. Ratio A PERCENT is a ratio that compares a number to 100. You can write a percent as a FRACTION, DECIMAL, or a number followed by a % sign. 40 100.40 40%  This is the way we normally write percents.

3. Changing Decimals to Percents To change a decimal to a percent, move the decimal place two places to the RIGHT [same as multiplying by 100].4 = 40%.04 = 4%.004 =.4 % 1.2 = 120%

4. Changing a Fraction to a Percent To change a Fraction to a Percent: Divide the TOP by the BOTTOM Numerator = 4 Denominator 10 [Remember the TOP number goes into the Calculator 1 st ] 10/4 =.4.4 = 40%

5. Try these Percents.80.08 1.890 80 100 4 5

6. Writing Equations for Percents Objective: Write equations to solve problems involving percents.

7. Main Idea We can write an equation to find the percent of a number. We will change the words of a statement into math symbols. IS  EQUALS [ = ] Of  MULTIPLY [ * ]

8. Example IS  EQUALS [ = ] Of  MULTIPLY [ * ] What number is 20% of 750? x = 20 * 750 x =.20 * 750 x = 150

9. Example 2 IS  EQUALS [ = ] Of  MULTIPLY [ * ] What percent of 80 is 4? x * 80 = 4 80 80 x =.05 5%

10. Practice P. 186 # 1-10, 13-1-27 *Show your work!

11. Sales Tax Discount is a PERCENTAGE off of a price. [Subtract] Tax is a Percentage added to the price. [Add]

12. Example. Neiman Marcus has a sale. There is a 10% discount for all items purchased in the store. If you buy a coat for $100, how much do you have to pay? 10% off of a $100 coat is how much?.10 * 100 = x The discount is $10. Regular price of the coat: $100 - $10 (discount) = $90

13. Example. You buy a coat at Neiman Marcus for $100. There is a 6% sales tax added to the price. How much does the coat cost? $100 *.06 = $6 Original Price + Sales tax = final price $100 + $6 = $106

14. Practice P.186 #11,12.