The formula for the volume of a pyramid is: Volume=(1/3)*(Area of the base)*(Height of the pyramid) You stated that the pyramid has a 10 by 10 base, so the "area of the base" is 100 squared feet. Also, you stated that the "height of the pyramid" is 8.5 feet. So, Volume=(1/3)(100 squared feet)(8.5 feet) V=(1/3)(850 cubic feet) V=283.33333..... cubic feet