Question

IfS and T are two sets such that S has 21 elements, T has 32 elements,and

S∩T has 11 elements, how many elements does S ∪T have?

Answer 1

It is given that:

n(S)= 21, n(T)= 32, n(S∩T) = 11

We know that:

n(S ∪T) = n(S) + n(T) – n(S ∩T)

∴ n(S ∪T) = 21 + 32 – 11 = 42

Thus,the set (S ∪T) has 42 elements.