Common Fractions

Add and subtract common fractions

Adding and Subtracting Fractions

To add or subtract fractions, they must have the same denominator (bottom number). If they already match, just add or subtract the numerators (top numbers).

Example

Same Denominator

2/5 + 1/5 = 3/5 (add numerators, keep denominator) 7/8 − 3/8 = 4/8 = 1/2 (subtract numerators, simplify) 3/4 + 1/4 = 4/4 = 1 whole

Example

Different Denominators

1/2 + 1/4 = ? Convert 1/2 to 2/4 (multiply top and bottom by 2) 2/4 + 1/4 = 3/4 ✓ 1/3 + 1/6 = ? Convert 1/3 to 2/6 2/6 + 1/6 = 3/6 = 1/2 ✓

Note

Remember

You can only add or subtract fractions when the denominators are the same. Find a common denominator first. Always simplify your answer if possible.

Key Vocabulary

NumeratorThe top number of a fraction (parts we have)

DenominatorThe bottom number of a fraction (total equal parts)

Common denominatorA shared bottom number for two fractions

SimplifyReduce a fraction to its simplest form

Equivalent fractionsFractions that have the same value (e.g. 1/2 = 2/4)

SASL Avatar

Loading avatar...

1 / 5

Numerator

Speed: