Locate the towns in question and the bar scale on the map.
Use your ruler to measure the length of the bar scale and notice how many miles it corresponds to. For example, let's say the scale is 1.5 inches long and corresponds to five miles.
Measure the distance between the two towns with your ruler. For this example, let's say it's six inches from one town to the other.
Divide your result from Step 3 by the length of the scale. In this case, you would divide six by 1.5 for a result of four.
Multiply the number you obtained in Step 4 times the length in miles to which the scale corresponds. In this example, we would multiply four (the result from Step 4) times five (the number of miles represented by 1.5 inches) for a result of 20. Therefore, in our example, it is approximately 20 miles from one town to the other.