Answer
Measure the number of inches on the map between the two cities, and multiply that number of inches by the number of miles represented by 1 in.
Work Step by Step
By definition, SCALE is the ratio of the lenght in a drawing (or model) to the length of the real thing.
Example: If the scale is 1:10 then anything with the size of 1 would have a size of 10 in the real world, so a measurement of 150mm on the drawing would be 1500mm in the real world.
