Given:
Altitude = 3 miles
Let's determine how far from the farmhouse the airplane will be if it has travelled 4 miles at the same altitude.
The figure below represents this situation:
To find the distance, apply pythagorean theorem:

Where:
a = 3 miles
b = 4 miles
Thus, we have:

Take the square root of both sides:
![\begin{gathered} \sqrt[]{c^2}=\sqrt[]{25} \\ \\ c=5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/ndfyoovsbntesk0hgtmbf28x9we0braec9.png)
Therefore, the distance between the airplane and the farmhouse is 5 miles.
ANSWER:
5 miles