Subtracting Fractions with Like Denominators

When two fractions have the same (like) denominator, subtracting them is simple: subtract the numerators and keep the denominator the same. The denominator tells you the size of the pieces, and since both fractions use the same size pieces, only the count changes. If you are still getting comfortable with fractions, review what fractions are first.

To work out a difference such as 5/8 − 2/8: subtract the numerators (5 − 2 = 3), keep the denominator (8), which gives 3/8. Then simplify the result if you can. For 6/8 − 2/8 = 4/8, both numbers share a factor of 4, so 4/8 reduces to 1/2.

• 7/10 − 3/10 = 4/10, which simplifies to 2/5.
• 9/12 − 5/12 = 4/12, which simplifies to 1/3.
• 3/4 − 1/4 = 2/4 = 1/2.

Subtracting works exactly like adding fractions with like denominators, just with a minus instead of a plus.

This shortcut only works when the denominators match. If they are different, you first rewrite the fractions with a common denominator — see subtracting fractions with unlike denominators.

Related lessons

• Basic Math