How long a ladder must you have to reach the top of a 15-foot wall if the bottom of the ladder is placed 4 feet from the base of the wall? Round to the nearest tenth of a foot.

The wall and ground form the two legs of a right triangle, and the ladder is the hypotenuse. Use the Pythagorean theorem: ladder length = √(15² + 4²) = √241 ≈ 15.5 feet. So the correct choice is 15.5 ft.

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