Question

In a group of 30 persons, 18 take tea. Find how many take coffee but not tea, if each person takes atleast one of the drinks.

Answer 1

Let, the no of persons who drinks tea$=n\left(T\right)=18$

Let,No of person who drinks coffee $=n\left(C\right)$

No of persons $=n(T\cup C)$

No of person who drinks coffee only $=n(C-T)$

A.T.Q,

$n(C-T)=n(T\cup C)-n\left(T\right)$

$⟹n(C-T)=30-18=12$