# Percent

Percents. Means “per 100”.  It tells you a ratio “out of 100”. If there are 80% of the people in a school with black hair, then for every 100 people in the school, 80 of them have black hair.
Percents can be written as fractions by placing the number over 100 and simplifying.

A Decimal fraction is a fraction (as 25/100) in which the denominator is a power of 10.

Recall that a percent shows a part out of 100   (a percent is a decimal fraction with a denominator of 100). A percent means how many for each 100.

So 100% means the complete quantity, 50% means ‘half of’ and 25% means ‘a quarter of’.

Thus, if we know any two of these three quantities, it is easy to calculate the third one.

There are three basic types of percent problems:

Type 1: Finding the Percent (%) or Rate

Type 2: Finding the Part Type 3: Finding the Base or Whole Example: From a group of 30 students 50% are taking math. The number of students taking Math is  30 x 50/100 = 15    (half of 30)

To get the value of a percent of something, simply multiply the starting value (in this case 30 students) by the percentage over 100 (50/100 = 0.5).
Percent formula
Example: 4% of 50 is____ or 50 x 4% = 50 X 0.04 = 2
Example: 10% of X is 15, find X   X*10%=15   X=15/10% = 15/0.10=150
Percent change
Percentage change between two numbers A & B can be calculated as:  (B-A)/A * 100  For example, if a game price increases in value from \$10 to \$12 the percentage increase is:  (12-10)/10 * 100 = 2/10 *100 = 0.2*100 = 20 percent  Alternatively, if a game price decreases in value from \$10 to \$9  the percentage decrease is:  (10-9)/10 * 100 = 0.1*100 = 10 percent

### PE14    Percent_to_Decimal

Create a graphic organizer (Frayer Model) for the following vocabulary words: Percent, Percent of change, Percent Increase, Percent Decrease, Tax, Commission, Tip, Mark-up, Discount.