Answer:
64 miles
Explanation:
The distances will obey the proportion ...
actual distance / map distance = (48 mi)/(2.4 in)
So, the distance of interest is ...
(Da to Co)/(3.2 in) = (48 mi)/(2.4 in)
Multiplying by 3.2 in gives ...
Da to Co = (48 mi)(3.2/2.4) = 64 mi
The distance from Dayton to Columbus is 64 miles.
_____
Map proportions are often written with the actual distance in the denominator. That adds an extra step to the solution process. The proportion still holds when the ratios are written "upside down" or even "sideways", as, for example, ...
(Da to Co)/(48 mi) = (3.2 in)/(2.4 in)
If the unknown is written in the numerator, then finding its value is one step: multiplication by its denominator.