In ancient Egypt, Asher (Acenith's
assistant) is an apprentice rope stretcher
. He's preparing ropes to make a right triangle for laying out a good foundation, and is tying knots in the ropes at equal distances. He leaves one end of the rope unknotted so that each knot corresponds to one unit of length.
Assuming he's tied one rope with 3 knots, and one with 5, how many knots should he tie in the third rope to make a right triangle?