Question

Find the cardinality properties of n(G)=20, n(H)=30, n(G ∩ H) =5, find n(G ∪ H)

Answer 1

Using the inclusion/exclusion principle,

n(G U H) = n(G) + n(H) - n(G ∩ H) = 20 + 30 - 5 = 45