If S and T are two sets such that S has 21 elements, T has 32 elements, and `S cap T` has 11 elements, how many elements does `S cupT` have?

Explanation

n(S)=21, n(T)=32, n(S nn T)=11.

.n(S uu T)=n(S)+n(T)-n(S nn T)=21+32-11=53-1 k.

.therefore S uu T. has 42 elements.