Basic Math and Pre-Algebra For Dummies (48 page)

All the methods I describe earlier in this chapter work for both proper and improper fractions. Unfortunately, mixed numbers are ornery little critters, and you need to figure out how to deal with them on their own terms. (For more on mixed numbers, flip to Chapter
9
.)

I can't give you a direct method for multiplying and dividing mixed numbers. The only way is to convert the mixed numbers to improper fractions and multiply or divide as usual. Here's how to multiply or divide mixed numbers:

1. Convert all mixed numbers to improper fractions (see Chapter
   9
   for details).
   

   For example, suppose you want to multiply
   . First convert
   and
   to improper fractions:
   

   

2. Multiply these improper fractions (as I show you earlier in this chapter, in “Multiplying and Dividing Fractions” ).
   

   

3. If the answer is an improper fraction, convert it back to a mixed number (see Chapter
   9
   ).
   

   

   In this case, the answer is already in lowest terms, so you don't have to reduce it.
   

As a second example, suppose you want to divide
.

1. Convert
    and 
   to improper fractions:
   

   

2. Divide these improper fractions.
   

   Divide fractions by multiplying the first fraction by the reciprocal of the second (see the earlier “Multiplying and Dividing Fractions” section):
   

   

   In this case, before you multiply, you can cancel out factors of 11 in the numerator and denominator:
   

   

3. Convert the answer to a mixed number.