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1.Set Theory
easy
If $A$ and $B$ are disjoint, then $n(A \cup B)$ is equal to
A
$n(A)$
B
$n(B)$
C
$n(A) + n(B)$
D
$n(A)\,.\,n(B)$
Solution
(c) Since $A$ and $B$ are disjoint, $\therefore A \cap B = \phi $
$n(A \cap B) = 0$
Now $n\,(A \cup B) = n(A) + n(B) – n(A \cap B)$
$ = n(A) + n(B) – 0$$ = n(A) + n(B)$.
Standard 11
Mathematics
