If the price of a gallon of gas increases from $3.20 to $3.68, what percent did it increase?

To find the percent of increase, subtract the second number from the original/first number (3.68-3.2=0.48) and divide that result by the original number \(\frac{\mathrm{0.48} }{\mathrm{3.20} } = 0.15 \) = 15%