Round Robin tournament problem

I will show & explain what I have tried.
ans round robin.jpeg
So I realised i have to use combination,
I tried out several possibilities and look for pattern
I realise that from 15C2 to 16C2 there will be an increase of 15 games that needs to be played. (does it mean there were 15 teams before?)
does it mean just an additional 1 team?
.
.
But I am also confused with the initial statement that says a total of 21 games to be played, which refers to 7C2, meaning 7 teams participated in the beginning?
there is a big gap from 7 teams to 16 teams.
Please help me point out what I miss.
Thank you very much :)
 
This is a math help forum where helper assist students with their problems. What helpers never do is answer questions for students.
Please read the forum's posting guidelines to learn how to make an appropriate post.
 
This is a math help forum where helper assist students with their problems. What helpers never do is answer questions for students.
Please read the forum's posting guidelines to learn how to make an appropriate post.
relax, i was posting what I've done too, but i took some time.... I know the rules. thanks.
my attempt was posted before your warning post anyway too.
 
I will show & explain what I have tried.
View attachment 33851
So I realised i have to use combination,
I tried out several possibilities and look for pattern
I realise that from 15C2 to 16C2 there will be an increase of 15 games that needs to be played. (does it mean there were 15 teams before?)
does it mean just an additional 1 team?
.
.
But I am also confused with the initial statement that says a total of 21 games to be played, which refers to 7C2, meaning 7 teams participated in the beginning?
there is a big gap from 7 teams to 16 teams.
Please help me point out what I miss.
Thank you very much :)
Why look for the a difference of 15? Why not just add 21 and 15 to get 36. Now solve xC2=36

Maybe you are correct. 15=7+8. Done.
 
Somehow I saw 1 instead of 109 for the number of posts you made. Sorry about that.
 
Why look for the a difference of 15? Why not just add 21 and 15 to get 36. Now solve xC2=36

Maybe you are correct. 15=7+8. Done.
I am able to find x which is 9
8C2 = 28 (meaning 28 games played)
9C2 = 36 (meaning 36 games played)

can you explain the reasoning?
I am still thinking about how the initial 21 games to be played.
 
Oh wait does this have something to do with timeline, as in once the round robin is complete for early entries, then the late comers do their own round robin tournament? i was thinking as whole, all combined
 
If that is the case, 7C2 =21 (that means 7 teams in the beginning)
then late entries arrived, 6 teams came late so 6C2 = 15 (15 games played for late entries team only)
so a total of 13 teams? is my reasoning correct?
 
You can think as if all the 21+15 = 36 teamss were there at the start of the tournament.

If you solve xC2 = 36 you will get x=9, just as you did.
Think what you would have done if they never mentioned the 15 late comers and just said that there were 36 teams.
 
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Each team plays every other team once. In the end that is what happened. Even if the 21 teams played each other once and then the late arrival teams come and in the end each team played each other team once, does it really matter if some teams came late? What if the way the scheduled was made first the 21 teams played each other and then the remaining teams were included in the rest of the games?
 
Here is how I got 9 teams from 7+8 = 15
1 game was played between the 2 new teams (two teams because 7 and 8 are two numbers) and each new team played the 7 original teams once. This adds up to 15 additional games. Since there must have been 7 original teams and then two more late arriving teams, there must have been 9 teams in total.
 
when you say teams, you mean the games (the match right?)
I got the explanation
so 7 teams in the beginning, thus they play 21 games.
2 late comers entered, so additional 15 games added
total of 9 teams participating now
thus 9C2 = 36 (which correlates to 21 games +15 games too)
so answer is 9

is this it?
Thank you so muchhhhh for explaining till the end.
 
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