# Creating non reoccuring random groups of people

We have a group of 100 students that are meant to have discussion amongst each other. For this we want to separate them into 10 groups of 10 people. We want to have three rounds of discussions, however we want the groups to be different each time. No one person should get to sit with the same person twice.

Say we assign our groups letters abcdefghij (10) Person1 gets Round1:A Round2:B Round3:C Person2 gets Round1:A but then can't have Round2:B or Round3:C because they would then meet again.

The "output" I need is that each participant will recieve a card telling him at which table to sit in which round.

Doing this by hand sounds pretty insane and I'm sure there is a pretty simple solution for this. Maybe even a program that does exactly this, but I just can't find it or don't know what to search for...

Maybe this can even be done in excel or sth like that?

Please keep in mind I have NO CLUE about mathematics. So please try and make the answers understandable for the average math idiot ;)

All help or tips apreciated. Thanks for taking the time!

• This is an instance of what is called "the social golfer problem". Type that into the internet, and see what comes up. – Gerry Myerson Apr 30 '15 at 9:55
• Oh wow that was actually quite fascinating. So basically I have a "social golfer problem" but I have a lot more "golfers" The way it looks now we have 120 people divided into 15 tables thus giving us 8 people per table. I found a social golfer problem solver on wolfram demonstrations project but this only allowed up to 4 golfers per group. are there any other calcs out there? – David Apr 30 '15 at 10:29

$$\begin{array}{ccc}A & B & C \\ D & E & F \\ G & H & I\end{array}$$
So if you connect the following diagonals: $(A,E,I)$,$(B,F,G)$ and $(C,D,H)$, that still gives you three different groups from the ones before. Just extend the principle to the 10 by 10 matrix.