Q7 of 71 Page 30

Let A and B be two finite sets such that n(A – B) = 30, n(A ∪ B) = 180. Find n(B).


Given, n(A–B) = 30, n(A ∪ B) = 180.


It can be concluded that,


(A ∪ B) = (A–B) + B


∴ n(A ∪ B) = n(A–B) + n(B)


180 = 30 + n(B)


n(B) = 180 – 30 = 150.


Hence, n(B) = 150.


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