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

• \[\frac{1}{3}\]

• \[\frac{1}{4}\]

• \[\frac{5}{12}\]

•  \[\frac{2}{3}\]

Answer 1

\[\frac{2}{3}\] 

\[\text{ We know that the bag contains 5B (black), 4W (white) and 3R (red) balls }. \]
\[\text{ Now} , \]
\[P\left( B \right) = \frac{5}{12}\]
\[P\left( R \right) = \frac{3}{12}\]
\[P\left( B\text{ or } R \right) = P\left( B \right) + P\left( R \right)\]
\[ = \frac{5}{12} + \frac{3}{12}\]
\[ = \frac{8}{12} = \frac{2}{3}\]