Post on 01-Jan-2016
RatioA 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.
40100
.40
40% This is the way we normally write percents.
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%
Changing a Fraction to a PercentTo change a Fraction to a Percent:
Divide the TOP by the BOTTOM
Numerator = 4Denominator 10
[Remember the TOP number goes into the Calculator 1st]
10/4 = .4
.4 = 40%
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 [ * ]
ExampleIS EQUALS [ = ] Of MULTIPLY
[ * ]
What number is 20% of 750?
x = 20 * 750
x = .20 * 750
x = 150
Example 2IS EQUALS [ = ] Of MULTIPLY [
* ]
What percent of 80 is 4?
x * 80 = 4
x * 80 = 4 80 80
x = .05 5%
Sales TaxDiscount is a PERCENTAGE off of a price.
[Subtract]
Tax is a Percentage added to the price. [Add]
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
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