Question

10. If n(A) = 10, n(AUB) = 25 and n(An B) = 6, then n(B) =
a) 18
b) 19
c) 20
d) 21

Answer 1

n(AUB) =n(A) +n(B) -n(A ∩ B)

25=10+n(B) -6

25-4=n(B)

n(B) =21

option d) 21 is the right answer