Question

Daca card(A)=36,card(B)=52 si card(AB)=74,aflati card(AB).

Answer 1

$Voi~nota~card(X)=|X|. \\ \\ |A \cap B|=|A|+|B|-|A \cup B|. \\ \\ Deci~|A \cap B|=36+52-74 \Leftrightarrow \boxed{ |A \cap B|=14} ~ .$

Answer 2

Desenez diagrama Venn.

Notez :
 
card(A ∩ B) = y

card(A) =x+y

card(B) = y+z

Avem :

card(AUB) = x+y+z=74

card(A) =x+y = 36

card(B) =y+z = 52

Din aceste trei ecuatii determinam, relativ simplu, y = 14