In a B school there are 15 teachers who teach marketing or finance. Of these, 8 teach finance and 4 teach both marketing and finance. How many teach marketing but not finance ?
A.
15
B.
20
C.
11
D.
none of these
Answer :
11
Solution :
From the given condition $$n\left( {M \cup F} \right) = 15,\,\,n\left( F \right) = 8,\,\,n\left( {M \cap F} \right) = 4$$
$$\eqalign{
& {\text{So, }}n\left( {M \cup F} \right) = n\left( M \right) + n\left( F \right) - n\left( {M \cap F} \right) \cr
& {\text{or, }}n\left( M \right) = n\left( {M \cup F} \right) + n\left( {M \cap F} \right) - n\left( F \right) \cr
& {\text{hence }}n\left( M \right) = 15 + 4 - 8 = 11 \cr} $$
Releted MCQ Question on Calculus >> Sets and Relations
Releted Question 1
If $$X$$ and $$Y$$ are two sets, then $$X \cap {\left( {X \cup Y} \right)^c}$$ equals.