Question

Two balls are drawn at random with replacement from a box containing 10 black and 8 red balls. Find the probability that first ball is black and second is red. 

Answer 1

\[\text{ Given : Box } = \left( 10B + 8R \right) \text{ balls } \]

\[ P\left( \text{ first black and second red } \right)\]
\[ = \frac{8}{18} \times \frac{10}{18}\]
\[ = \frac{80}{324} = \frac{20}{81}\]