Apratim R. answered 01/23/23
Plus-n-Minus Tutoring
The base of the tetrahedron is an equilateral triangle with area
B = (sqrt(3) / 4) s^2
As you have noted, the tetraheedron has height h = sqrt(2 / 3) s.
So the tetrahedron has volume
V = (1 / 3) B h = (sqrt(2) / 12) s^3.
In particular, when s = 6, we have V = 18 sqrt(2) ≈ 25.46.