P = {3, 9, 11, 13} and Q = {3, 7, 9, 15} are subset of the universal set ξ = {1, 3, 7, 9, 11, 13, 15} find PI ∩ QI

Answer Details

First, let's find P^I, which is the complement of P in ξ: P^I = ξ \ P = {1, 7, 15} Similarly, Q^I = ξ \ Q = {1, 11, 13} The intersection of P^I and Q^I is the set of elements that are in both sets. In this case, the intersection is: P^I ∩ Q^I = {1} Therefore, the answer is option (C) {1}.