Basic Math and Pre-Algebra For Dummies (62 page)

Now suppose you want to convert the fraction
to a percent. Follow these steps:

1. Convert
   to a decimal by dividing the numerator by the denominator:
   

   

   Therefore,
   .
   

2. Convert 0.625 to a percent by moving the decimal point two places to the right and adding a percent sign (%):
   
   • 0.625 = 62.5%
     

When you know the connection between percents and fractions, which I discuss earlier in “Converting to and from Percents, Decimals, and Fractions,” you can solve a lot of percent problems with a few simple tricks. Other problems, however, require a bit more work. In this section, I show you how to tell an easy percent problem from a tough one, and I give you the tools to solve all of them.

 A lot of percent problems turn out to be easy when you give them a little thought. In many cases, just remember the connection between percents and fractions, and you're halfway home:

• Finding 100% of a number:
  Remember that 100% means the whole thing, so 100% of any number is simply the number itself:
  
  • 100% of 5 is 5.
    
  • 100% of 91 is 91.
    
  • 100% of 732 is 732.
    
• Finding 50% of a number:
  Remember that 50% means half, so to find 50% of a number, just divide it by 2:
  
  • 50% of 20 is 10.
    
  • 50% of 88 is 44.
    
  • 50% of 7 is
    (or
    or 3.5).
    
• Finding 25% of a number:
  Remember that 25% equals
  , so to find 25% of a number, divide it by 4:
  

  

• Finding 20% of a number:
  Finding 20% of a number is handy if you like the service you've received in a restaurant, because a good tip is 20% of the check. Because 20% equals
  , you can find 20% of a number by dividing it by 5. But I can show you an easier way: Remember that 20% is
  2 times 10%, so to find 20% of a number, move the decimal point one place to the left and double the result:
  

  

• Finding 10% of a number:
  Finding 10% of any number is the same as finding
  of that number. To do this, just move the decimal point one place to the left:
  

  

• Finding 200%, 300%, and so on of a number:
  Working with percents that are multiples of 100 is easy. Just drop the two 0s and multiply by the number that's left:
  

  

  (See the earlier “Dealing with Percents Greater than 100%” section for details on what having more than 100% really means.)