We know that the side L of the base of the pyramid is 20.6 in.
We also know that the slant height S is 91.1 in.
We have to find the height of the pyramid.
We can draw a cut of the pyramid, as if we were seeing it from one of the faces:
Then, we can apply the Pythagorean theorem to find H:
Answer: The height of the pyramid is 90.4 in.