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# Combinatorics, kaplan, 700 level, PS - unique 2 latter code

Author Message
Manager
Joined: 10 Jan 2011
Posts: 232

Kudos [?]: 81 [1], given: 25

Location: India
GMAT Date: 07-16-2012
GPA: 3.4
WE: Consulting (Consulting)
Combinatorics, kaplan, 700 level, PS - unique 2 latter code [#permalink]

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16 Oct 2011, 11:03
1
KUDOS
00:00

Difficulty:

(N/A)

Question Stats:

38% (00:24) correct 63% (00:29) wrong based on 17 sessions

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Each runner during a race is labeled with a unique one-letter code or a unique two-letter code, where the two letters are different. The codes use the 26-letter English alphabet, and if a given two letter code is used then the reverse code is not used. What is the maximum number of runners that can receive unique codes for the race?

A 325
B 351
C 677
D 650
E 676

_________________

-------Analyze why option A in SC wrong-------

Last edited by 144144 on 17 Oct 2011, 01:39, edited 1 time in total.
Moved to the right place

Kudos [?]: 81 [1], given: 25

Manager
Joined: 21 Aug 2010
Posts: 186

Kudos [?]: 133 [1], given: 141

Location: United States
GMAT 1: 700 Q49 V35
Re: Combinatorics, kaplan, 700 level, PS - unique 2 latter code [#permalink]

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19 Oct 2011, 11:53
1
KUDOS
nishtil wrote:
Each runner during a race is labeled with a unique one-letter code or a unique two-letter code, where the two letters are different. The codes use the 26-letter English alphabet, and if a given two letter code is used then the reverse code is not used. What is the maximum number of runners that can receive unique codes for the race?

A 325
B 351
C 677
D 650
E 676

1. 26 one letter code can be given(equal to number of alphabets)
2. Two letter codes

Number of possible 2 letter codes is equal to the sum of all the numbers between 25 and 1 (sum first 25 digits)

i.e, n(n+1)/2 = 325

Maximum number of runners that can receive unique codes = 325+26 =351
Ans B
_________________

-------------------------------------

Kudos [?]: 133 [1], given: 141

Re: Combinatorics, kaplan, 700 level, PS - unique 2 latter code   [#permalink] 19 Oct 2011, 11:53
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