Last modified on 5 June 2009, at 12:46

Prealgebra for Two-Year Colleges/Appendix (procedures)/Finding equivalent fractions

Equivalent fractions represent the same number, although they are written differently. For example,

\frac{1}{2} and \frac{2}{4}

represent the same amount.

You can find and equivalent fraction by multiplying the numerator and denominator by the same number. For example,

\frac{1}{2} = \frac{1 {\color{Red} \times 2}}{2 {\color{Red} \times 2}} = \frac{2}{4}

and

\frac{1}{2} = \frac{1 {\color{Red} \times 3}}{2 {\color{Red} \times 3}} = \frac{3}{6}

and

\frac{1}{2} = \frac{1 {\color{Red} \times 4}}{2 {\color{Red} \times 4}} = \frac{4}{8}.


When you are adding fractions or subtracting fractions, you will want to find an equivalent fraction with a certain denominator. For example,

\frac{3}{5} = \frac{\color{Blue}\mathrm{?}}{45}

In this case, you can see that you need to multiply the numerator and denominator by 9, because 45 divided by 5 is 9. So

\frac{3}{5} = \frac{3{\color{Red}\times9}}{5{\color{Red}\times9}} = \frac{\color{Blue}27}{45}.


You are also allowed to divide the numerator and denominator by the same number. We usually call this reducing fractions.