Question

A bag contains 3 red balls, 5 black balls and 4 white balls. A ball is drawn at random from the bag. What is the probability that the ball drawn is: 

black?

Answer 1

\[\text{ Number of red balls } = 3\]
\[\text{ Number of black balls } = 5 \]
\[\text{ Number of white balls }= 4\]
\[\text{ Total number of balls } = 3 + 5 + 4 = 12\]
\[\text{ Therefore, the total number of cases is } 12 . \]

\[\text{ Since there are 3 red balls, the number of favourable outcomes is 3 } . \]
\[P\left( \text{ a red ball } \right) = \frac{\text{ Number of favourable cases }}{\text{ Total number of cases }} = \frac{3}{12} = \frac{1}{4}\]