Math

Adding Fractions by Adding the Denominators

Adding straight across the top and bottom instead of finding a common denominator first.

Quick check

Why students make it

Addition feels like it should work the way multiplication does, where you do go straight across. Fractions need a common denominator first, and that step is easy to skip.

The rule done right

Rewrite both fractions over a common denominator, then add only the numerators and keep the denominator the same.

Related resources

fractionsarithmetic