Two balls are drawn at random with replacement from a box containing 12 black and 9 red balls. Find the probability that first ball is black and second is red.

\(\frac{12}{49}\)

Black ball in bag = 12

total ball in bag = 21

  probability that first ball is black =\(\frac{12}{21}\) =\(\frac{4}{7}\)

  Ball has been replaced.

Now, red balls in bag = 9

 total balls in bag = 21

  probability that second ball is red =   \(\frac{9}{21}\) =\(\frac{3}{7}\)

Probability of getting first ball black and second red = \(\frac{4}{7}\) × \(\frac{3}{7}\)

= \(\frac{12}{49}\)