Percentages
% are always out of 100
We use a % sign
Percentages can be converted to decimals and fractions easily:
  • Changing a dec to a %: multiply by 100
  • Changing a percentage to a fraction: put the % over 100, then simplify if necessary
  • Changing a percentage to a dec: just multiply by 100
  • Changing a fraction to a dec: just divide the top number by the bottom number (in your calculator)
  • Changing a dec to a frac: check what column the last digit is in and put it over that number Eg: 0.35, the 5 is in the 100th column so we write 35/100 (then simplify to 7/20)
  • Changing a frac to %: change frac to a dec, then multiply it by 100

Example: Shoes are marked as $180, but they are in a 30% off sale. What is the new price of the shoes? In your calculator you would enter: 30 ÷ 100 x 180 = __. Then you would subtract that percentage from $180.
The shoes will cost $180-$54 = $126

Example 2: Find 10% by moving the decimal point left one place – 10% of $180 is $18
So, 30% of 180 is ($18 x 3) $54

Try to fill out the table below:
Decimal
Fraction
Percentage
0.5
½
50%

1/4
25%
0.2

20%
0.3


0.4

40%


10%
0.05
1/20
5%
0.03




150%
0.35



67/100


1/8


1/3

0.125



3/8