Question

A bag contains 4 red, 5 black and 6 white balls. A ball is drawn from the bag at random. Find the probability that the ball drawn is:

 red or white 

Answer 1

\[\text{ Number of red balls }= 4\]
\[\text{ Number of black balls }= 5\]
\[\text{Number of white balls }= 6\]
\[\text{ Total number of balls in the bag } = 4 + 5 + 6 = 15\]
\[\text{ Therefore, the total number of cases is 15 } . \]

\[\text{ Let D denote the event of getting a red or a white ball }. \]
\[P\left( D \right) = \frac{\text{ Number of favourable outcomes }}{\text{ Total number of outcomes }} = \frac{4 + 6}{15} = \frac{10}{15} = \frac{2}{5}\]