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Same colored balls

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Same colored balls

by gmatrant » Thu Nov 10, 2011 11:36 pm
A bag contains six marbles: two red, two blue, and two green. If two marbles are drawn at random, what is the probability that they are the same color?

Is the below approach correct

No of ways of choosing 2 balls of the same colour is to choose one of the 3 sets = 3 ways
Total ways of choosing 2 balls is 6c2 = 15 ways

probability of choosing 2 of the same colour is 3/15 => 1/5.
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by shankar.ashwin » Fri Nov 11, 2011 12:32 am
yes, 1/5 is correct.

Another way of looking at it, pick up any ball in the first pick, now out of the remaining 5, you have one 1 ball of the same color.
So probability would be 1/5.
Last edited by shankar.ashwin on Fri Nov 11, 2011 12:45 am, edited 1 time in total.
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by satishchandra » Fri Nov 11, 2011 12:37 am
gmatrant wrote:Is the below approach correct
No of ways of choosing 2 balls of the same colour is to choose one of the 3 sets = 3 ways
Total ways of choosing 2 balls is 6c2 = 15 ways
1/5 is correct.
Your approach is correct
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