Question

Suppose that the number of elements in set $A$ is $p$, the number of elements in set $B$ is $q$ and the number of elements in $A \times B$ is $7$ then $p^{2}+q^{2}=$_____

• A. 50
• B. 42
• C. 51
• D. 49

Answer 1

Answer: (A)

$n ( A )= p , n ( B )= q$
$n ( A \times B )=7$
$pq =7$
$p ^{2}+ q ^{2}=7^{2}+1^{2}$ or $1^{2}+7^{2}$
$p ^{2}+ q ^{2}=50$