Aright square pyramid has a height of 4" and a base of 6" and a slant height twice the pyramids height. what is the volume of the pyramid?

pyramid height 4"
base 6" and
slant height 8"
Pyramid height^2 = slant height^2 - (base / 2) ^ 2
Pyramid height^2 =64 -9
Pyramid height = 7.4161984871"
Pyramid Volume = (Area of the Base * Height) ÷ 3
Pyramid Volume = (36 * 7.4161984871) / 3
Pyramid Volume = 88.9943818451 cubic feet
(89 cubic feet rounded)
Source:http://www.1728.org/volpyrmd.htm