There is some data:

A, B, C (where C = A/B)
10, 20, 0.5
10, 100, 0.1

There are two ways of counting the average C:

- First is sum(A)/sum(B), that gives C equal 20/120=0.1666

This is Tableau: sum([A])/sum([B])

- Second is avg(C), that gives C equal (0.5+0.1)/2=0.3

This is in Tableau: No Idea...

Both have different usages. I need the second one, but can't find a way to calculate it. Anything I try, I always get the first type.