Image showing the scale of the map written in three ways. First way is 1 inch : 30 miles where 1 inch is for drawing and 30 miles is for actual size. The second way is the fraction 1 inch over 30 miles. The third way is 1 inch = 30 miles.

Start with the scale of the drawing in centimeters over actual in meters and write a proportion so that 1 over 1.5 = 3 over n. Write cross products, so that 1n = 1.5 times 3. Simplify to get n = 4.5.

Image of a map of North Carolina and a ruler in centimeters. The map locates the cities Winston-Salem, Raleigh and Charlotte and has a scale of 1 centimeter : 75 kilometers.

Start by writing the proportions of the map and actual sizes, so that 1 over 75 = 1.6 over n. Write cross products so that 1 n = 75 times 1.6. Simplify to get n = 120.