Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

In how many ways can $8$ people be divided into

  1. $4$ groups of $2$ people

  2. First pair, second pair. Third pair and the fourth pair

How do you go about doing this question?

share|cite|improve this question
    
Are you familiar with binomial coefficients? What have you tried? – Jeremy Nov 2 '12 at 9:21

4 groups of 2 people:

  _ _      _ _      _ _      _ _
( 8.7/2! * 6.5/2! * 4.3/2! * 2.1/2! )/4!

First pair, second pair. Third pair and the fourth pair:

1º pair -> 8*7/2! = 28
2º pair -> 6*5/2! = 15
 ...    ->   ...

understood?

share|cite|improve this answer
    
Use consistent notation, please. – Cameron Buie Nov 2 '12 at 10:53

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.