Addition and Subtraction of Mixed Numbers 7-2
Although there are two methods discussed in our textbook, I would like students to concentrate on using the 'Stacking Method' rather than changing mixed numbers into improper fractions.
In the stacking method, we work separately with the fractional and whole- number parts of the given mixed numbers. Sometimes, we must change the form of a mixed number before we can subtract the fractional part, as with the following example
9 3/7 - 4 5/7 re write
69 3/7
-4 5/7
______
9 3/7 = 8 + 7/7 + 3/7 so re write the first line as 8 10/7
r8 10/7
-4 5/7
______ and now you can easily perform the subtraction
4 5/7
If the fractional parts of the given mixed numbers have different denominators, we must find equivalent mixed numbers whose fractional parts have the same denominator-- usually the LCD. You can use the box method for finding the LCM to find the LCD here!!
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