To find the number of miles you would be above sea level after 4 hours, you start at 1.55 miles and end at 0.75 miles.
To find the total change in miles:
1.55 miles - 0.75 miles = 0.80 miles
This means you would cover a vertical distance of 0.80 miles in 4 hours. To find the miles per hour, you divide this distance by the time taken:
\[ \text{Miles per hour} = \frac{0.80 \text{ miles}}{4 \text{ hours}} = 0.20 \text{ miles per hour} \]
So, the average rate of change in elevation is 0.20 miles per hour.