A map uses a scale where 1 inch represents 25 miles. If two cities are 4.5 inches apart on the map, how far apart are they in reality?

Set up a proportion using the scale: 1 inch / 25 miles = 4.5 inches / x miles. Cross-multiply: 1 × x = 25 × 4.5, so x = 112.5 miles. Scale and proportion problems are solved by writing the known ratio equal to the unknown ratio and cross-multiplying. Here each inch is 25 miles, so 4.5 inches is simply 4.5 × 25 = 112.5 miles. Always keep the units consistent (inches with inches, miles with miles) when setting up the proportion, and the cross-multiplication gives the missing value directly.