:: 5 x 6 = 30 ::
So what that we do it against a backdrop of triangles instead of squares?
Triangles are simpler and we're allowing for all edges the same length, same as squares, so that's no advantage on the square's side.
Take your two lengths, A and B, and just connect a line across, and you're done. That's your area, in equilateral triangular units.
An interesting feature of pouring fluids into such containers is you may tilt it to have the water level connect A and B.
When filling a tetrahedron, your corners A, B and C may be independently reached as well.
So if the goal is to measure out a number that's factorable, into two or three terms, you've got a way of tilting to get that: get the fluid to hit all the factors in the flask, as calibrated along the edges.
Think of it as a kind of beaker, amidst other lab equipment. Tilt the tetrahedron to 4 x 5 x 3 for 60 tetrahedron's worth of liquid. Scale those unit tetrahedrons to be milliliters if you like, no one's stopping you.
