1. PERCENTS

2. WHAT ARE PERCENTS?  We’ve done lots of work with fractions and decimals. We’ve determined that fractions that denominators of 100 are useful because they can easily be written as decimals. Another useful way to express a fraction with a denominator of 100 is to use a special symbol called the percent symbol-- %  Percent means “out of 100”

3. CHANGING FRACTIONS TO PERCENTS  Let’s start practicing changing fractions to percents. We’ll start with fractions that already have a denominator of 100.  19/100  37/100  58/100  22/100  5/100  3/100

4. CHANGING FRACTIONS TO PERCENTS (CONT.)  If the denominator of a fraction can easily be changed to 100, do that to change the fraction to a percent. Let’s try it.  1/2  3/5  9/10  15/20  32/50  90/1000  35/500

5. CHANGING FRACTIONS TO PERCENTS (CONT.)  If you are working with a fraction that cannot easily be converted to an equivalent fraction whose denominator is a power of 10, change the fraction to a decimal first to change it to a percent.  Remember, to change a fraction to a decimal, you divide the numerator by the denominator.  Once you have the decimal, you multiply by 100 to get the percent. A shortcut for multiplying by 100 is to move the decimal point 2 places to the right.  Let’s try this with 5/6.

6. CHANGING FROM A PERCENT TO A FRACTION  To write a percent as a fraction, just remember that percent means out of 100.  52% means 52 out of 100. You can write this as 52/100.  Finally, simplify if possible.  What is the final answer?  Let’s change the following percents to fractions.  23%205%  18%45%  60%72%

7. CHANGING FROM A PERCENT TO A DECIMAL  To change a percent to a decimal, you do the opposite of what you would do to change a decimal to a percent—divide by 100 or move the decimal point two places to the left.  If there is no decimal point in the percent, you assume that it comes after the last digit of the percent.  Let’s write these percents as decimals.  99%5%  56.3%8%  24%235%