Definition
A common denominator is a shared denominator that two or more fractions can use. It is needed when adding or subtracting fractions with different denominators.
To compare or combine slices from pizzas cut differently, you need to re-cut them all into the same number of slices first. That shared number of slices is the common denominator.
Examples
- To add 1/3 + 1/4, use common denominator 12: 4/12 + 3/12 = 7/12.
- 1/2 and 1/6 have a common denominator of 6.
- 2/5 and 3/10 have a common denominator of 10.