Answer: the ladder should be 25 feet
Explanation:
The ladder forms a right angle triangle with the building and the river. The length of the ladder represents the hypotenuse of the right angle triangle. The height from the top of the ladder to the base of the building represents the opposite side of the right angle triangle.
The distance from the bottom of the ladder to the base of the building represents the adjacent side of the right angle triangle.
To determine the length of the required ladder h, we would apply Pythagoras theorem which is expressed as
Hypotenuse² = opposite side² + adjacent side²
h² = 24² + 7² = 576 + 49
h² = 625
h = √625 = 25 feet