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Team

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Intern
Joined: 04 Jan 2011
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Team [#permalink]  06 Jan 2011, 07:13
00:00

Difficulty:

5% (low)

Question Stats:

50% (02:28) correct 50% (00:55) wrong based on 10 sessions
There are, in a certain league, 20 teams, and each team face another team for a total of 10 times. How many games are played in the season?

a) 1800
b) 3600
c) 2400
d) 180
e) 5400

[Reveal] Spoiler:
OA SHOULD be A but I don't get how
[Reveal] Spoiler: OA
Manager
Joined: 19 Jul 2009
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Location: baltimore, md
Schools: kellogg, booth, stern, ann arbor
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Re: Team [#permalink]  06 Jan 2011, 09:05
unfortunately, i went the long way. it took about 2:20 to do.

since there are 20 teams, and each team plays the other team a total of 10 times, then the 1st team will play a total of 190 games (there are 19 other teams played 10 times each so 19*10 = 190), our second team will play a total of 180 games, our 3rd team will play 170.......
adding all of these up, we get 1800.

hopefully someone can post an answer that is shorter. i'm not the best with combination-type problems.

Master Bunuel might be able to provide a good explanation.
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Re: Team [#permalink]  06 Jan 2011, 11:28
It should be 1900

1st team:190
2nd team:180
3rd team :170

Similarly the last team will play 0

therefore(190+180+170....10)

10(19+18+17+16....1)

10 (n(n+1)/2)=10(19*20/2)=1900
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Re: Team [#permalink]  06 Jan 2011, 13:25
Derek1988 wrote:
There are, in a certain league, 20 teams, and each team face another team for a total of 10 times. How many games are played in the season?

a) 1800
b) 3600
c) 2400
d) 180
e) 5400

[Reveal] Spoiler:
OA SHOULD be A but I don't get how

Each possible pairing of 20 teams plays 10 times
There are C(20,2) pairings

So no of matches = C(20,2) * 10 = 190 * 10 = 1900
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Joined: 27 Jan 2010
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GMAT 2: Q V
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Kudos [?]: 19 [0], given: 53

Re: Team [#permalink]  25 Feb 2011, 11:50
Derek1988 wrote:
There are, in a certain league, 20 teams, and each team face another team for a total of 10 times. How many games are played in the season?

a) 1800
b) 3600
c) 2400
d) 180
e) 5400

[Reveal] Spoiler:
OA SHOULD be A but I don't get how

Choose 2 teams out of 20 teams = 20C2 = 190 (sets that can be formed)
Each set of team plays 10 games = 190 * 10 = 1900.
Current Student
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Re: Team [#permalink]  25 Feb 2011, 22:39
Should be 1900! Can the original poster please clarify the answer again and the source ?
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Re: Team [#permalink]  25 Feb 2011, 23:49
I remember for such problems we perhaps need to divide the total number of games by 2, as two teams play each other, so isn't that true here, or am I missing something ?

Regards,
Subhash
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Re: Team   [#permalink] 25 Feb 2011, 23:49
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