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Question
A bag contains 5 black balls, 4 white balls and 3 red balls. If a ball is selected randomwise, the probability that it is black or red ball is
Options
\[\frac{1}{3}\]
\[\frac{1}{4}\]
\[\frac{5}{12}\]
\[\frac{2}{3}\]
Solution
\[\frac{2}{3}\]
\[\text{ We know that the bag contains 5B (black), 4W (white) and 3R (red) balls }. \]
\[\text{ Now} , \]
\[P\left( B \right) = \frac{5}{12}\]
\[P\left( R \right) = \frac{3}{12}\]
\[P\left( B\text{ or } R \right) = P\left( B \right) + P\left( R \right)\]
\[ = \frac{5}{12} + \frac{3}{12}\]
\[ = \frac{8}{12} = \frac{2}{3}\]
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