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27 Oct 2009, 23:29
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This question doesn't come from GMAT text book. It just popped up in my mind during my study.
Given a set of letters (A,B,C), how many combinations of 4 letters are there, using both A and C at least once? You don't have to use all of them. Besides, (AACC), (CCAA),(ACAC),(CACA),(CAAC) and (ACCA) are all considered same.
I am kind of comfused during the caliculation. pLease help me.
Given a set of letters (A,B,C), how many combinations of 4 letters are there, using both A and C at least once? You don't have to use all of them. Besides, (AACC), (CCAA),(ACAC),(CACA),(CAAC) and (ACCA) are all considered same.
I am kind of comfused during the caliculation. pLease help me.
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28 Oct 2009, 00:54
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yuskay
Let me put it this way if I got it right:
We have 3 letters A,B and C. We want to form 4 letter combination from this letters, with condition that:
1. Order doesn't matter.
2. We should use at least once A and C, but not necessarily B.
How many such combinations are possible?
If it's so then, let's fix TWO letters AC, as they always should present.
We can easily right down all the possibilities.
Fixed AC as we must use them and any 3 left letter from the set:
ACAA
ACAB
ACAC
ACBB
ACBC
ACCC
28 Oct 2009, 02:47
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Bunuel, thank you!
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
