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There are 8 teams in a certain league and each team plays each of the [#permalink]

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03 Dec 2009, 01:07

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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?

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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03 Dec 2009, 07:35

its 8C2 that means [(Factorial 8)] / [ (Factorial 2)(Factorial 6) ] added OG tag

ro86 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?

1.15 2.16 3.28 4.56

OA is 28

I am not able to understand the explanation given to me in the OG. The OG has calculated the answer as (8x7)/2. has the og used some formula to arrive at the answer.

Tho i got the answer through manual counting. can any 1 explain the process used in the OG.

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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03 Dec 2009, 07:49

ro86 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?

1.15 2.16 3.28 4.56

OA is 28

I am not able to understand the explanation given to me in the OG. The OG has calculated the answer as (8x7)/2. has the og used some formula to arrive at the answer.

Tho i got the answer through manual counting. can any 1 explain the process used in the OG.

this is nothing but application of direct formulae i.e combination ( if one is aware of this) the formula is if we are asked to select r items out of n items then we can say nCr=n!/[(n-r)!*(n!)] now in this q to play a match we need 2(r) teams out of 8(n) teams substituting we get 8!/[2!*6!]=8*7*6!/[2!*6!]=8*7/2=28 HTH _________________

GMAT is not a game for losers , and the moment u decide to appear for it u are no more a loser........ITS A BRAIN GAME

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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03 Dec 2009, 07:54

2

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This is just applying the idea of choosing combinations i.e. in how many ways can you choose 2 teams from a total 8. You can readily apply the formula for choosing 2 out of 8 as \(= (8x7)/2 = 28\)

The explanation would be something like: Essentially, we need to find all possible pairs of teams from the 8.

So to create a pair, the first team can be chosen from the total of 8 - so 8 options/ways available. Now for each of this, we can choose the the opponent team for the pair from the 7 teams left. So the total will be \(8 x 7 = 56.\)

Now you can see that when we do the above, we will all possible pairs - (team1, team2), (team2, team3)....etc. We will also get the reverse pair (team2, team1), (team3, team2).... The order shouldn't matter since a game is just between 2 teams irrespective of the order.

So for every such pair of team, the reverse order is also included in the total of 56. So the total number of unique pairs we can have (which is the number of games) \(= 56/2 = 28\).

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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24 Jul 2011, 02:03

I was so confused by this line "If each game is played by 2 teams, what is the total number of games played?

I got 28 (coz 7!) then when I see this line "If each game is played by 2 teams, what is the total number of games played?" I took one extra step to divide 28/2 = 14......although 14 is not a choice but I wonder can ayone pls explain what does this line mean?

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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25 Jul 2011, 10:05

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You can use combinations or you can do the following (note that this often comes up as something called "the handshake problem" as well as in counting the number of diagonals in convex polygons).

Team 1: plays 7 other teams - 7 games Team 2: plays 7 other teams, but you already counted their game against team 1 - 6 games Team 3: plays 7 other teams, but you already counted their games against teams 1 and 2 - 5 games And so on

7 + 6 + 5 + 4 + 3 + 2 + 1 = 28

If there are x people in a room, then for everyone to shake hands with everyone else exactly once there will be (x(x-1))/2 handshakes. Same method with the polygon problem.

Re: There are 8 teams in a certain league and each team plays each of the [#permalink]

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05 Feb 2015, 03:49

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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?

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