Question

There are 4 white and 5 red (indistinguishable) balls in a bag. Suppose you draw one ballout at a time without replacement and stop when you have drawn all the white (4 white) orall the red (5 red) balls. What is the probability that the last ball you drawn was a whiteball?

Answer 1

5/9

Explanation:

What we have in this question are four white balls and 5 red balls.

This is the sample space

[(4w,0R) (4w,1R)(4w,2R)(4w,3R)(4w,4R)(0w,5R)(1w,5R)(2w,5R)

So we have 9 possible sets of events

The event number with the last ball being white = 5

Probability of the last ball drawn being white = 5/9

= 0.56