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combinations

by CITI29 » Thu Jul 10, 2008 8:03 am
LEAGUE RESULTS
Team -Number of Games Won
A -4
B -7
C -9
D -2
E -2
X -?

According to the incomplete table above, if each of
the 6 teams in the league played each of the other
teams exactly twice and there were no ties, how
many games did team X win? (Only 2 teams play in
a game.)
(A) 4
(B) 5
(C) 6
(D) 8
(E) 10

pls advise?
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by spanlength » Thu Jul 10, 2008 8:09 am
Since there were 30 matches in total ,hence total no. of win must be 30.
Since the 5 teams hav won 24 matches hence X team must have won 6 times.
My Ans is C)6

Plz give OA.
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by CITI29 » Thu Jul 10, 2008 8:41 am
hi ,

thats the correct answer. But how do u know 30 total games?..its said that each team played with each other team exactly twice. So how did u reach 30?

pls explain
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by dbart06 » Thu Jul 10, 2008 8:55 am
6 teams, each plays a total of 10 games = 60 total games.

you have to remember that some games are duplicated

ie. ab,ac, ad, ae, ax.......ba, bc,bd,be,bx .. because of the duplication you divide the total number of games 60 by 2, this gives 30 diferent games total.


hope it helps
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by preetha_85 » Thu Jul 10, 2008 10:10 am
Hi .

To find the total no. of games since they r 6 teams nd 2 teams play with each other take it as 6C2. This gives 15.since they play each other twice multiply this by 2 i.e 15*2=30.. nd hence 30 games in all
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Permutation

by evansbd » Thu Jul 17, 2008 7:29 am
Why cant you use the permutation equation instead of combination muliplied by two or counting outcomes then dividing by two?

Permutation = 6!/(6-2)! = 30
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Re: Permutation

by BlueRain » Thu Jul 17, 2008 4:24 pm
evansbd wrote:Why cant you use the permutation equation instead of combination muliplied by two or counting outcomes then dividing by two?

Permutation = 6!/(6-2)! = 30
Because it is awkward to explain it that way? It's just saying why can't you just multiple by 10 and then divide by 2*5... :?

The difference between 6C2 and 6P2 is just 2, so you end up dividing 2 anyway. The point is the order does not matter when picking teams to play in a game, so combination makes more sense.
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