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

thelazyman

Junior Member
Joined
Jan 14, 2006
Messages
58
Hi, the question asks.

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
Joined
Jan 29, 2005
Messages
8,259
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

Guest

Guest
is it 2^10 - 10?
 

pka

Elite Member
Joined
Jan 29, 2005
Messages
8,259
Anonymous said:
is it 2^10 - 10?
Actually it is \(\displaystyle \L
2^{10} - 11\)

Think about why 11!
 
G

Guest

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

cool, thanks
 
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