SOLUTION: Two balls were placed in a box. Each ball was equally likely to be red or green. We know that at least one of the balls is red. The probability that both of the balls are red i

Question 1155502: Two balls were placed in a box. Each ball was equally likely to be red or green.
We know that at least one of the balls is red.
The probability that both of the balls are red is
Answer by ikleyn(52756) (Show Source): You can put this solution on YOUR website!
.


The sample space is this set


    1)  RR   with the probability 

    2)  RG   with the probability 

    3)  GR   with the probability 

    4)  GG   with the probability 


We know that at least one ball is red.


It leaves us only 3 possibilities 1), 2) and 3).


Of these 3 possibilities, only one is favorable (#1).


Therefore, the conditional probability under the problem's question is


    P( both red | at least one is red) =  = .    ANSWER

Solved.

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On conditional probability, see the lessons
- Conditional probability problems
- More conditional probability problems
in this site.

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