You may have been thinking of $\displaystyle{4}\frac{{{1}}}{{{2}}}\usepackage{cmbright}\Huge\$ gallons. Multiply: $\displaystyle{4}\frac{{1}}{{2}}\ \text{ quarts}\cdot\frac{{{2}\ \text{ pints}}}{{{1}\ \text{ quart}}}\usepackage{cmbright}\Huge\$ . The correct answer is 9 pints.