Fraction rules
Multiplying and Dividing Fractions:
- Common denominators are NOT needed.
- Always change mixed numbers to improper fractions.
- CANCEL (reduce) between any numerator and any denominator
if you can, but cancel only when a multiplication sign is
present: Never cancel when you have a division sign.
- TO MULTIPLY: Multiply numerator times numerator,
denominator times denominator. Reduce answer to a mixed
number in lowest terms.
- TO DIVIDE: Change the divide sign to a multiplication
sign, then invert the second fraction and multiply as in
Step 4.
Adding and Subtracting Fractions:
- Common (like) denominators are necessary, so change all
unlike fractions to equivalent fractions with like
denominators. To make equivalent fractions, multiply the
numerator and denominator by the same number.
- Keep mixed numbers; DO NOT change mixed numbers into
improper fractions.
- Add (or subtract) the numerators, put the numerator
answer over the common denominator. If any improper
fractions arise in the answer, change the improper
portion to a mixed number.
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