Percentage increase = (Increase ÷ Original) × 100%.<br><br>&bull; Increase = \(\$2.25 - \$1.80 = \$0.45\)<br>&bull; Percentage = \(\frac{0.45}{1.80} \times 100\% = \frac{1}{4} \times 100\% = 25\%\)<br><br>Final Answer: 25%