What is the square feet of 36 inches by 60 inches?

Answer 1

There is really no such thing as "the square feet of...". The people who use that
term for it are those who are unclear on the concept, and who often know not
whereof they speak, and along about the time I hear it for the 8th time in the same
day, my baloney alarm begins to tingle and the fuzz along my spine stands up on
end. It's not a pleasant experience.

What you want is the area of that place. There are hundreds of ways it could be
described ... acres, hectares, sections, cm2 ... but right now, you want it described
in square feet.

36 inches = 3 feet
60 inches = 5 feet

Area = (length) x (width) = (3 feet) x (5 feet) = 15 square feet.