Two balls are drawn at random with replacement from a box containing 7 black and 4 red balls. Find the probability that first ball is black and second is red.
Answer & explanation
Correct answer: option 4
Total number of balls = 11
number of black balls =7
number of red balls = 4
probability of getting first ball black = 7/11
the ball is replaced after the first draw.
So, probability of getting second ball as red = 4/11
Therefore, the probability of getting first ball as black and second ball as red = (7/11) x (4/11)
= 28/121