This is the problem link.
The first two parts build the tempo. Once you solve these two(please don't see the solution), move to the last part.
If six numbers are chosen at random, uniformly and independently, from the interval [0,1], what is the probability that they are the lengths of the edges of a tetrahedron?
My attempt -
Once I have chosen such which form a triangle, number of points lying inside that triangle will be proportional to the number of tetrahedrons.
I don't really know how to follow next, or if what I did until now is any helpful or not.