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# If each of the 12 teams participating in a certain tournament plays ex

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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
Bunuel wrote:
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23

total possible matches in tournament ; 12 c2 ; 66
IMO C
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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This ques reminds me of formula of number of handshakes between people.

- Say n be number of teams. n = 12
- Total number of matches: $$\frac{n(n-1)}{2 }=> \frac{12*11}{2} = 66$$

Option C!
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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Bunuel wrote:
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23

The number of games played is 12C2 = 12! / (2! x 10!) = (12 x 11) / 2 = 66.

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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
parkhydel wrote:
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23

PS28101.02

Every team plays 11 games so total number of games should be 12*11 but since in a match two teams are involved we half the obtained number.
Hence total matches = $$\frac{12*11}{2}$$ = 66

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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
parkhydel wrote:
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23

PS28101.02

Asked: If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

Number of games which will be played = 12C2 = 66

IMO D
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
Total number of different matches = $$^{12}C_{2}$$ = $$\frac{12*11}{2}$$ = $$66$$
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
For someone who doesnt know about combination formulae:

consider 4 teams A B C D

Listing down number of matches for these 4 teams as per the given conditions:

AvA - a team cannot play against itself
AvB
AvC
AvD
Number of matches: 3

BvB - a team cannot play against itself
BvC
BvD
Number of matches : 2

CvC - a team cannot play against itself
CvD
Number of matches : 1

DvD - a team cannot play against itself
Number of matches : 0

Total number of matches: 3+2+1+0=6
For 4 teams, number of matches as per given conditions is: 3+2+1 i.e (4-1)+(4-2)+(4-3)+(4-4)=3+2+1+0=6

You can calculate for any number of teams using this approach: Use Arithmetic Progression of common difference 1 for a higher number of teams as First term will be (Number of teams-1) and last term would be 1

For the given problem:
Total number of matches= 11+10+9+...+1 = {(11+1)*11}/2 = 66
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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Solution:

Number of games that can be played exactly one game with each of the other teams

= 12 C 3 (We select two teams of 12 and hence use combination)

=66 (option c)

Hope this helps

Devmitra Sen(GMAT Quant Expert)
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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Bunuel wrote:
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23

PS28101.02

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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
If each of the 12 teams participating in a certain tournament plays exactly one game with each of the other teams, how many games will be played?

A. 144
B. 132
C. 66
D. 33
E. 23
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
In a tournament with 12 teams, each team plays exactly one game with each of the other teams. To determine the total number of games played, we can use the combination formula.

The number of ways to choose 2 teams from a set of 12 teams is given by the combination formula:

C(12, 2) = 12! / (2! * (12-2)!) = (12 * 11) / (2 * 1) = 66.

Therefore, there will be 66 games played in the tournament.

Hence, the correct answer is C. 66.
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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Re: If each of the 12 teams participating in a certain tournament plays ex [#permalink]
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