The scale of the map is 1 centimeter = 15 kilometers, which we can write as the following unit rate.
15 kilometers/1 centimeter
By multiplying this unit rate by 15, we get the number of kilometers that corresponds to 15 centimeters on the map.
15 kilometers* 15/1 centimeter* 15=225 kilometers/15 centimeters
As we can see, the actual distance is 225 kilometers.
