Logical question (no variations, permutations or combinations)

  • #1
Physicsissuef
908
0

Homework Statement



How many contestants have on one chess tournament, if every person have played only one game with all of the other contestants separately, and there are 210 games played.

This problem should not be solved by variations, permutations or combinations. This problem should be solved by using the quadric equation. (we should put some condition, and out of there make some quadric equation).

Homework Equations




The Attempt at a Solution



I have no idea.

x- the number of players

I really don't know.
 

Answers and Replies

  • #2
armis
103
0
The answer just popped up into my head. Don't know how to explain it :confused:

[tex] \sum^x_{N=1} N-1 = 210 [/tex] x is the number of participants
 
Last edited:
  • #3
HallsofIvy
Science Advisor
Homework Helper
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The answer just popped up into my head. Don't know how to explain it :confused:

[tex] \sum^x_{N=1} N-1 = 210 [/tex] x is the number of participants
Then how do you know it is the answer?

If there are n contestants then, for each one, there are n- 1 "other contestants" and so each plays n-1 games. n people, each playing n-1 games, means there are n(n-1) games- except that each game involves two players: there are actually n(n-1)/2 games played. Since there were a total of 210 games, n(n-1)/2= 210.

(Which is, by the way, exactly what armis is saying!)
 
  • #4
armis
103
0
Oh, exactly. Thanks HallsofIvy
 
  • #5
Physicsissuef
908
0
I understand. Thank you.
 

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