You can add fractions if the denominators are the same. You simply add the numerators.
If the fractions have different denominators, determine the lowest common denominator (LCD) so that you can express each fraction in equivalent form. The lowest common denominator is the lowest number that the denominator of each individual fraction will divide into.
Mixed numbers need to be converted to improper fractions before using this addition technique.
Converting mixed numbers to improper fractions
Subtracting fractions is very similar to adding in that all fractions
in your calculation need to have the same denominator. You may need to
determine the lowest common denominator (LCD) as you did with addition.
Multiplication of fractions is carried out by multiplying all the numerators together and all the denominators together.
Sometimes the answer to a multiplication calculation can be simplified by dividing both numerator and denominator by the same number. This process is called cancelling, because you strike out the original numbers to create the new fraction.
To divide by a fraction, invert it and multiply.
Complete this fractions activity sheet (Word 93 kb)