question_answer 28)

Two balls are drawn at random with replacement from a box containing 10 black and 8 red balls. Find the probability that (i) both balls are red. (ii) first bal is black and second is red (iii) one of them is black and other is red  

Answer:

Black balls = 10  n(B) = 10       Red balls = 8  n (R) = 8       Total balls = 10 + 8 = 18                                    (i)P (both balls are red) = P (RR) = P(R) P(R)        events rare independent]       (i)     P (first ball black and second red)              = P(BR) = P(B) P (R)              events are independent]                         (iii) P (one black and other red)                         = P(BR or PB)                         = P(BR) + P(RB)                          BR and RB are mutually exclusive]             = P(B) P(R) + P(R), P(B)             independent]