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# There are 5 identical Blue balls & 7 identical red

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Senior Manager
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There are 5 identical Blue balls & 7 identical red [#permalink]

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25 Sep 2003, 06:13
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

There are 5 identical Blue balls & 7 identical red balls. Find the number of ways in which 2 balls can be selected.
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25 Sep 2003, 06:43
Since there are no restrictions on the taken balls, the answer should be 12C2.
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25 Sep 2003, 06:49
caught in the trap...
try again.
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25 Sep 2003, 07:31
Does 12A2 means permutations..?
if yes, its wrong.
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25 Sep 2003, 08:06
This seems too easy to be right, but, sine you can't tell the balls a part besides the color red and blue

one blue and one red
one red and one bule
one red and one red
one blue and one blue

for a total of 4
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25 Sep 2003, 09:48
i would say 3 ways....assuming BR and RB are the same
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26 Sep 2003, 04:23
thats correct. Answer is 3 ways.
We must remember that nCm is the number of ways m objects can be selected when there are n distinct objects. For identical objects we need to actually work it out.
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02 Jul 2004, 07:42
I was looking back on some old comb/perm problems, and had a question on this old post....

Why would the answer to this question be 3 instead of 4? If it is asking for the "number of ways" doesn't that indicate permutation, in which case order matters? Therefore, wouldn't we want to treat Blue/Red and Red/Blue as two distinct cases?

Therefore, four ways:
RR
BB
BR
RB

Can someone help? Thanks!
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02 Jul 2004, 07:47
gotta agree with guy 123 br and rb are the same thing..if the question hada stem askin us to pick the color r or b first or in some order then the answer wud have been different but it dont specify that.
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02 Jul 2004, 08:01
Ok... I see your point. Thanks!
02 Jul 2004, 08:01
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# There are 5 identical Blue balls & 7 identical red

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