Find the cardinal number of the indicated set. Use the cardinal number formula.
-If $n ( A ) = 8 , n ( B ) = 21$ and $n ( A \cup B ) = 25$, what is $n ( A \cap B )$ ?
A) 4
B) 12
C) 6
D) 2

Question

Quizplus · Accepted Answer

4The formula for finding the number of elements in the intersection of two sets given the number of elements in each set and their union is $n(A \cap B) = n(A) + n(B) - n(A \cup B)$. Plugging in the given values, we get $n(A \cap B) = 8 + 21 - 25 = 4$.

Find the Cardinal Number of the Indicated Set n(A)=8,n(B)=21n ( A ) = 8 , n ( B ) = 21n(A)=8,n(B)=21

Find the Cardinal Number of the Indicated Set $n ( A ) = 8 , n ( B ) = 21$