Q76 / 180 · KCET 2019 · Mathematics
If \( U \) is the universal set with \( 100 \) elements; \( A \) and \( B \) are two sets such that \( n(A)=50, n(B)=60 \),
\( n(A \cap B)=20 \) then \( n\left(A^{\prime} \cap B^{\prime}\right)= \)
\( n(A \cap B)=20 \) then \( n\left(A^{\prime} \cap B^{\prime}\right)= \)
- A\( 20 \)
- Correct answerB\( 10 \)
- C\( 40 \)
- D\( 90 \)
Solution
$(B)$
$n(U)=100$
$n(A)=50$
$n(B)=60$
$n(A \cap B)=20$
$n(A \cup B)=n(A)+n(B)-n(A \cap B)$
$=50+60-20$
$=110-20$
$=90$
$n\left(A^{\prime} \cap B^{\prime}\right)=n(A \cup B)^{\prime}$
$=n(U)-n(A \cup B)$
$=100-90$
$=10$
Hence, the correct answer is option: 'B'.