Question

A box contains 24 identical balls out of which 12 are white and 12 black the balls are drawn at random from the box one at a time with replacement the probability that a wide ball is drawn for the 4th time on the 7th is

Answer 1

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Answer 2

number of balls = 24

number of white balls = 12

number of non-white ball = 24 - 12 = 12

Find the probability of getting a white ball and a non-white ball:

P(white ball) = 12/24 = 1/2

P(non-white ball) = 12/24 = 1/2

In the first 6 draws, we will need to get 3 white balls:

P(3 white balls in 6 draws) = 6C3 x (1/2)³(1/2)³ = 5/16

Find the probability that the 7th draw is a white ball:

P(white ball) = 1/2

P(7th draw is a white) = (5/16) (1/2) = 5/32

Answer: The probability is 5/32