WAEC 2014 · Paper 2 · Q5

Events $A$ and $B$ are such that $P(A) = \frac13$ and $P(B) = \frac16$ . Find $P(A \cup B)$ if events $A$ and $B$ are:

Worked solution (try it first)

Independent: $P(A \cap B) = \frac13 \times \frac16$
$= \frac{1}{18}$ .
So $P(A \cup B) = \frac13 + \frac16 - \frac{1}{18}$
$= \frac{6 + 3 - 1}{18}$
$= \frac49$ .