Here are some simple lessons on operations with fractions.
MATH MILESTONE #B5: OPERATIONS WITH FRACTIONS
To summarize:
Like fractions are added by adding the numerators. Like fractions are subtracted by subtracting the numerators. The denominator remains the same. To add or subtract unlike fractions, one must convert them to like fractions first.
To convert unlike to like fractions, we first calculate the LCM (least common multiple) of all the unlike denominators. Then we calculate the equivalent fractions for unlike fractions with the LCM as the new denominator.
To multiply fractions, we simply multiply the numerators together to get the numerator of the product, and multiply the denominators together to get the denominator of the product. To divide by a fraction, we simply multiply by its reciprocal.
In general practice, a fraction in the final answer is expressed in its lowest terms. The lowest terms are obtained by taking all the common factors out of the numerator and the denominator.
A “division” notation is not the only notation possible to express fractions. Another way is to extend the place value notation to account for fractions. That notation is covered under the milestone on DECIMAL NUMBERS.
Here are some videos from Khan Academy on Fractions.
Adding and subtracting fractions
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