help with QR question from destroyer

[skim1988]

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Can somebody please help me with question #27 from 2011 DAT destroyer?

there are 12 members of the democratic party at a meeting. how many different groups of 3 members can be formed?

thanks!

 

[Potatochips]

Can somebody please help me with question #27 from 2011 DAT destroyer?

there are 12 members of the democratic party at a meeting. how many different groups of 3 members can be formed?

thanks!

12C3 = 12! / [(12-3)! * 3!] = (12 x 11 x 10) / (3 x 2 x 1) = 2 x 11 x 10 = 220 ways

 

[rockclock]

simple combinations:

12 C 3 = 12!/3!/(12-3)! = 220

 

[VDR]

The order of the members is not important for this type of problem. This is a combination problem.

n!/(n-r)! r! formula.

so basically, 12! / (12-8)! 8!

then broken down a bit more... 12x11x10/ 3x2
=220

i am not very good at this either but hope it helps.

 

[skim1988]

So how do we know whether to use permutation or combination to solve a problem? for example, permutation was used to solve this problem:

6 different people are running for 4 different positions. how many different committees can consist of these offices?

 

[little Buddy]

12*11*10/3*2*1 = 220. This is what Chad does and it makes it so much easier. Think combinations/permutations.

If there were four spots: 12*11*10*9/4*3*2*1 = 495

 

[little Buddy]

6*5*4*3/4*3*2*1 = 60

 

[skim1988]

12*11*10/3*2*1 = 220. This is what Chad does and it makes it so much easier.

Doesnt chad only have a video on trig? where can i access his video on permutation and combination?

 

[Dental2000]

Ok im confused

How do u know when to use n!/(n! x (n-r)!) and n!/(n-r)! ???

 

[little Buddy]

go to the quiz at the bottom and he has video answers...very legit. Below the physics quiz