If $n(A) = 5$, $n(B) = 7$ and $n(A \cap B) = 3$, then $n(A \cup B)$ equals

If $n(A) = 5$, $n(B) = 7$ and $n(A \cap B) = 3$, then $n(A \cup B)$ equals
  1. $9$
  2. $12$
  3. $15$
  4. $10$

Solution

$n(A \cup B) = n(A) + n(B) - n(A \cap B) = 5 + 7 - 3 = 9$.

Asked in: MH-SSC-9

Practice more Sets questions on Aicharya