Answer:
15 m
Step-by-step explanation:
The Pythagorean theorem tells you the length of the hypotenuse of a right triangle is the root of the sum of the squares of its legs. Here, the ladder forms the hypotenuse of a triangle with legs 9 m and 12 m, so has length ...
length = √((12 m)² +(9 m)²) = √(144+81) m = 15 m
The ladder is 15 m long.
