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Red and Yellow (Posted on 2024-04-16) Difficulty: 3 of 5
A bag contains an unknown number of red balls and yellow balls. When N balls are drawn at random (without replacement) the probability that they are all yellow is 1/2. The number of balls in the bag is the minimum for this to happen.

If the first N balls were all yellow, what is the probability that the next ball drawn is red?

Express the probability as a function of N.

See The Solution Submitted by K Sengupta    
Rating: 4.5000 (2 votes)

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Solution Solution | Comment 1 of 7
For the given conditions of the problem, there must be 2N-1 yellow balls in the bag, and 1 red ball, for a total of 2N balls.  

After N yellow balls have been drawn from the bag, there are N remaining, one of which is red.  So the probability that the next ball drawn is red is 1/N.  



  Posted by tomarken on 2024-04-16 13:51:55
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