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Addition of fractions with different but related denominators

To add fractions with different denominators we must first convert them to equivalent fractions with the same denominators. At this level students work with related fractions.

\begin{align}\frac{3}{6} + \frac{3}{4} &= \frac{6}{12} + \frac{9}{12} \text{(convert each to equivalent fraction with same denominators)} \\&= \frac{15}{12} \\&= 1\frac{3}{12} \text{(convert the improper fraction to a mixed number)} \\&= 1\frac{1}{4} \text{(simplify)}\end{align}