I have a clearifying question about set theory formulas, if you all don't mind.
1. For 3 sets A, B, and C: P(AuBuC) = P(A) + P(B) + P(C) – P(AnB) – P(AnC) – P(BnC) + P(AnBnC)
2. No of persons in atleast one set = P(A) + P(B) + P(C) - P(AnB) - P(AnC) - P(BnC) + 2 P(AnBnC)
Why these two formulas are different? Isn't "at least in one set" equal to union of all (AuBuC)?
I think first one is good for at least one person as well.
No idea where can we use the second formula.