Question
Question: A box contains 24 identical balls of which 12 are white and 12 are black. The balls are drawn at ran...
A box contains 24 identical balls of which 12 are white and 12 are black. The balls are drawn at random from the box one at time with replacement. The probability that a white ball is drawn for the 4th time on the 7th draw is:
A
5/64
B
27/32
C
5/32
D
½
Answer
5/32
Explanation
Solution
Probability of getting a white ball at any draw is
The probability of getting a white ball 4th time in the 7th draw.= P (getting 3 white balls in 6 draws) x P (white ball at the 7th draw).
= 
.