A tennis coach divides her 9-player squad into three 3-player groups with each player in only one group. How many different sets of three groups can be made?
I have trouble with these too but I do believe you have doubled counted.
I am not sure what the answer is but maybe it is just what you have divided by 3! because the order the groups are selected in is of no consequence.
That would bring your answer down to 280.
I did this a different way and came up with 280 then too.
Do you know what the correct answer is ?