Basic Math and Pre-Algebra For Dummies (51 page)

In this problem, I subtract
. Then I subtract 7 – 3 = 4. Not too terrible, agreed?

One complication arises when you try to subtract a larger fractional part from a smaller one. Suppose you want to find
. This time, if you try to subtract the fractions, you get

Obviously, you don't want to end up with a negative number in your answer. You can handle this problem by borrowing from the column to the left. This idea is similar to the borrowing that you use in regular subtraction, with one key difference.

When borrowing in mixed-number subtraction,

1. Borrow 1 from the whole-number portion and add it to the fractional portion, turning the fraction into a mixed number.
   

   To find
   , borrow 1 from the 11 and add it to
   , making it the mixed number
   :
   

   

2. Change this new mixed number into an improper fraction.
   

   Here's what you get when you change
   into an improper fraction:
   

   

   The result is
   . This answer is a weird cross between a mixed number and an improper fraction, but it's what you need to handle the job.
   

3. Use the result in your subtraction.
   

   

   In this case, you have to reduce the fractional part of the answer: