SOLUTION: A bag contains 2 red balls and 2 green balls. A person randomly pulls out 2 balls. What is the probability that both balls are red?

Question 1210223: A bag contains 2 red balls and 2 green balls. A person randomly pulls out 2 balls.
What is the probability that both balls are red?
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52792) (Show Source): You can put this solution on YOUR website!
.

Sorry, I was wrong.

My solution was wrong.

I deleted it to keep the Internet clean.

Thanks for critics from other tutors.

Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

Tutor ikleyn has the same wrong answer to this problem as to the problem about the gold and silver earrings. If she would just look at her solutions and find the errors, she would not need to insist that all the other tutors who have responded to this and similar problems are wrong and she is right.

For this problem she labels the balls as R1, R2, G1, and G2, then writes out a list of 6 possible combinations of 2 of the balls: (R1,R2), (R1,G1), (R1,G2), (R2,R1), (R2,G1),AND (R2,G2). Then, since 2 of those 6 combinations contain both red balls, she says the probability that both balls are red is 2/6, or 1/3.

But her list of the 6 combinations is faulty. (R1,R2) is the same combination as (R2,R1); and the combination (G1,G2) is missing from her list.

So of the 6 correct possible combinations, only one contains both red balls.

And then the probability that both balls are red is 1/6.

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