Final answer:
After comparing the scales of the road and river by simplifying their ratios, it is clear that they are proportional, as both have the same ratio of 1 inch to 20 miles.
Step-by-step explanation:
The question asks if the scales given for a road and a river are proportional or not.
To determine this, we compare the ratios of map distances to real-life distances for both cases.
For the road, the ratio is 4 inches to 80 miles, which simplifies to 1 inch to 20 miles.
For the river, the ratio is 2.5 inches to 50 miles, which simplifies to 1 inch to 20 miles.
Since both ratios are equal, the road and river scales are indeed proportional.