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# Q2: A researcher plans to identify each participant in a

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SVP
Joined: 28 May 2005
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Q2: A researcher plans to identify each participant in a [#permalink]

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22 Oct 2005, 05:53
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Q2:
A researcher plans to identify each participant in a certain medical experiment with a code consisting of either a single letter or a pair of distinct letters written in alphabetical order. What is the least number of letters that can be used if there are 12 participants, and each participant is to receive a different code?
A. 4
B. 5
C. 6
D. 7
E. 8
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hey ya......

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SVP
Joined: 05 Apr 2005
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Re: PS # medical experiment [#permalink]

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22 Oct 2005, 06:25
5.

5 gives = 15 codes in alphabetical order.
4 gives = 10 codes in alphabetical order.

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Director
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22 Oct 2005, 11:11
1. 4 codes with A,B,C&D
A, B, C, D, AB, AC, AD, BC, BD, CD - TOTAL 10

2. 5 codes with A,B,C,D&E
A, B, C, D, E, AB, AC, AD, AE, BC, BD, BE, CD, CE, DE - TOTAL 15

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SVP
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23 Oct 2005, 14:02
Thank you. that helps.

is there any short cut for this type of problems?
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Senior Manager
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23 Oct 2005, 14:59
We can use the combination formula here for larger set. Basically we want to find out 'n' where n + nC2 >= 12

Since we need least number of letters, we can either start from choice A (answer is in ascending order) or start from C.

Hope this helps.

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23 Oct 2005, 14:59
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