 # Multiplying and Dividing Rational Numbers

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Multiplying and Dividing Rational Numbers

Rational Numbers The term Rational Numbers refers to any number that can be written as a fraction. This includes fractions that are reduced, fractions that can be reduced, mixed numbers, improper fractions, and even integers and whole numbers. An integer, like 4, can be written as a fraction by putting the number 1 under it.

Multiplying Fractions
When multiplying fractions, they do NOT need to have a common denominator. To multiply two (or more) fractions, multiply across, numerator by numerator and denominator by denominator. If the answer can be simplified, then simplify it. Example:

Simplifying Diagonally
When multiplying fractions, we can simplify the fractions and also simplify diagonally. This isn’t necessary, but it can make the numbers smaller and keep you from simplifying at the end. From the last slide: An alternative: 1 You do not have to simplify diagonally, it is just an option. If you are more comfortable, multiply across and simplify at the end.

Mixed Numbers To multiply mixed numbers, convert them to improper fractions first. 1

Sign Rules Remember, when multiplying signed numbers...
Positive * Positive = Positive. Negative * Negative = Positive. Positive * Negative = Negative.

Try These: Multiply Multiply the following fractions and mixed numbers:

Solutions: Multiply

Solutions (alternative): Multiply
Note: Problems 1, 2 and 4 could have been simplified before multiplying. 1 2 2 1 1 2 1 3 1 3

Dividing Fractions When dividing fractions, they do NOT need to have a common denominator. To divide two fractions, change the operation to multiply and take the reciprocal of the second fraction (flip the second fraction). Keep it-Change it-Flip it (multiply by the reciprocal) Change Operation. Flip 2nd Fraction.

Dividing Fractions Finish the problem by following the rules for multiplying fractions.

Try These: Divide Divide the following fractions & mixed numbers:

Solutions: Divide