# probability again (how many groups of at least 2 people...)

#### thelazyman

##### Junior Member

How many groups consisting of at least 2 people can be chosen from a group of 10 people?

I tried...

10!/2!2!2!2!2! Thinking that 5 groups can be formed but got the wrong answer.

#### pka

##### Elite Member
Re: probability again

thelazyman said:
How many groups consisting of at least 2 people can be chosen from a group of 10 people?
I am not doing this completely. Here are hints.
‘Groups’ in this context are subsets!
If there are N elements in a set, then there are 2<SUP>N</SUP> subsets of that set.
Now one of those sets is the empty set - the null-group no members.
There are N singletons set, subsets with only one element.
Now you combine those along with what you learned from the dice problem and finish it this off. Post your answer and we will check it.

G

is it 2^10 - 10?

#### pka

##### Elite Member
Anonymous said:
is it 2^10 - 10?
Actually it is $$\displaystyle \L 2^{10} - 11$$

G

total - 1 - 0
2^10 -10 -1

cool, thanks