You kind of hit on a solution to doubling a cube sit one next to it. But then you have changed it's shape and no longer a cube.
Take the third pyramid for instance 356.4 feet in length. If it were instead a cube and not a pyramid but on the same base with side 356.4 feet then it's volume = 45,270,270.014 cubic feet.
Double it x 2 = 90,540,540.29 cubic feet or the volume of the Great Pyramid with a height to the base of it's capstone.
To double a cube EXACTLY convert it to the shape of a pyramid.
Multiply the base by 3 x 356.4 = 1,069.2 feet and this is the diagonal of the base of the Great Pyramid. base = 756.0385704 feet.
Divide (by construction) the length of the base into 3 ever parts 356.4 / 3 = 118.8 then add ne ie multiply 118.8 x 4 = 475.2 feet this is the height of the pyramid.
Volume of pyramid base 756.0385704 squared 571,594.32 / 3 = 190,531.44 x height 475.2 = 90,540,540.29 cubic feet. The Great Pyramid.
When I first discovered this I worked the sum in Indus/Saxon feet 13.2 inches 356.4 imperial feet = 324 Indus/Saon feet but method is the same.
[flic.kr] note; scroll from right to left
Edited 2 time(s). Last edit at 22-Dec-17 21:27 by molder.