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OG 18, question-187

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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by vaibhav101 » Sun Oct 15, 2017 4:22 am
There are 8 teams in a certain league and each team plays each of the other teams exactly once. If each game is played by 2 teams, what is the total number of games played?

A. 15
B. 16
C. 28
D. 56
E. 64
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OG 18, question-187

by Brent@GMATPrepNow » Sun Oct 15, 2017 5:48 am
vaibhav101 wrote:There are 8 teams in a certain league and each team plays each of the other teams exactly once. If each game is played by 2 teams, what is the total number of games played?

A. 15
B. 16
C. 28
D. 56
E. 64
There are 8 teams. If we ask each team, "How many teams did you play?" we'll find that each team played 7 teams, which gives us a total of 56 games (since 8 x 7 = 56).

From here we need to recognize that each game has been COUNTED TWICE.
For example, if Team A and Team B play a game, then Team A counts it as a game, and Team B ALSO counts it as a game.

So, to account for the DUPLICATION, we'll divide 56 by 2 to get [spoiler]28 (C)[/spoiler]
--------------------------
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https://www.beatthegmat.com/soccer-time-t70860.html

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by Brent@GMATPrepNow » Sun Oct 15, 2017 5:52 am
vaibhav101 wrote:There are 8 teams in a certain league and each team plays each of the other teams exactly once. If each game is played by 2 teams, what is the total number of games played?

A. 15
B. 16
C. 28
D. 56
E. 64
We can also use counting techniques to answer this question.

The question is asking us to determine the number of different ways to select 2 teams to play a game.
Since the order in which we select 2 teams does not matter, we can use COMBINATIONS

We can select 2 teams from 8 teams in 8C2 ways
8C2 = 28

If anyone is interested, we have a free video on calculating combinations (like 8C2) in your head: https://www.gmatprepnow.com/module/gmat- ... /video/789

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by Scott@TargetTestPrep » Mon Dec 18, 2017 7:38 am
vaibhav101 wrote:There are 8 teams in a certain league and each team plays each of the other teams exactly once. If each game is played by 2 teams, what is the total number of games played?

A. 15
B. 16
C. 28
D. 56
E. 64
We are given that there are 8 teams in a league and that each game is played by 2 teams. Note that each team does not play itself and the order of pairing each team with its opponent doesn't matter. [For example, the pairing of (Team A vs. Team B) is identical to the pairing of (Team B vs. Team A).] The situation can therefore be solved by finding the number of combinations of 8 items taken 2 at a time, or 8C2:

8C2 = 8!/2!(8-2)!] = (8 x 7)/(2 x 1) = 56/2 = 28

Answer: C

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by Brent@GMATPrepNow » Mon Dec 18, 2017 7:46 am
vaibhav101 wrote:There are 8 teams in a certain league and each team plays each of the other teams exactly once. If each game is played by 2 teams, what is the total number of games played?

A. 15
B. 16
C. 28
D. 56
E. 64
There are 8 teams. If we ask each team, "How many teams did you play?" we'll find that each team played 7 teams, which gives us a total of 56 games (since 8 x 7 = 56).

From here we need to recognize that each game has been COUNTED TWICE.
For example, if Team A and Team B play a game, then Team A counts it as a game, and Team B ALSO counts it as a game.

So, to account for the DUPLICATION, we'll divide 56 by 2 to get 28

Answer: C

Cheers,
Brent
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