Though pyramids were built from the beginning of the Old Kingdom to the close of the Ptolemaic period in the fourth century A.D., the peak of pyramid building began with the late third dynasty and continued until roughly the sixth (c. 2325 B.C.)
There are four major categories of informative speeches, defined after the main focus of a speech.
Informative speeches could be about:objects,events,processes andconcepts.
This particular informative speech would be about a concept.
Concepts in informative speeches are whatever is considered more abstract, as they deal with rather abstract topics such as theories, ideas and beliefs.
Here we have theories about how the Great Pyramid of Giza was built so it is safe to say this informative speech would be about a concept.
I do not believe researchers are certain, but are fairly sure.
The Great Pyramid of Giza was built for the Fourth Dynasty Pharaoh Khufu (or Cheops), and was completed around 2560 BCE.
This is mathematics, I think you meant to put this in History, lol. I hope my answer helps. I'm not sure if it was the answer you were looking for though. :)