Writing a rational number using a decimal point is called the decimal expansion of that rational number. Since $$\frac{a}{b} = a \div b$$ the decimal expansion of rational numbers whose denominators cannot be directly written as a power of 10 is found by dividing the numerator of the fraction by its denominator.

Examples:

• $$ \frac{3}{4}= \frac{3 \cdot 25}{4 \cdot 25} = \frac{75}{100} = 0.75 $$ or

\[
\begin{array}{c,c}
\begin{array}{c}
\quad &30 \;\;\;\;\\
-\quad &28 \;\;\;\; \\
\hline
\;\;\quad &0\phantom{.} 20\\
-\quad \;\;\quad &0\phantom{.} 20\\
\hline
\;\;\quad &0\phantom{.} 0\\\end{array}
\begin{array}{|c}
\quad 4 \\
\hline
\quad 0.75
\\
\\
\\
\\
\end{array}
\\
\\
\\
\\
\end{array}
\]