A bag has 4 red, 6 black balls.

Question

A bag has 4 red, 6 black balls. A ball is drawn, its colour observed, returned with 2 more of the same colour. A second ball drawn --- find the probability it's red.

Accepted Answer

$$P(R_2) = \frac{4}{10}\times\frac{6}{12}+\frac{6}{10}\times\frac{4}{12} = \frac{2}{5}$$

Solutions · 1