Question

If and T are two sets such that has 21 elements, T has 32 elements, and ∩ T has 11 elements, how many elements does ∪ T have?

Answer 1

It is given that: n( ) = 21, n(T) = 32, n( ∩ T) = 11

We know that: n ( ∪ T) = n ( ) + n (T) – n ( * ∩ T)

∴ n ( * ∪ T) = 21 + 32 – 11 = 42

Thus, the set ( * ∪ T) has 42 elements.