waecmaths question:
A bag `contains 4 red and 6 black ball of the same size. If the ball are shuffled briskly and two ball are drawn one after the other without replacement . Find the probability of picking ball of different colours
Option A:
$\tfrac{8}{15}$
Option B:
$\tfrac{13}{25}$
Option C:
$\tfrac{11}{15}$
Option D:
$\tfrac{13}{15}$
waecmaths solution:
\[\begin{align} & \Pr (R\text{ and }B)=\frac{4}{10}\times \frac{6}{9}=\frac{4}{15} \\ & \Pr (B\text{ and }R)=\frac{6}{10}\times \frac{4}{9}=\frac{4}{15} \\ & \Pr (R\text{ }and\text{ }B)+\Pr (B\text{ and }R)=\frac{4}{15}+\frac{4}{15}=\frac{8}{15} \\\end{align}\]
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