Posted by **Anna** on Monday, April 4, 2011 at 5:29pm.

Please help-I'm really mixed up

How do I find the permutations of the first 12 letters taken 3 at a time?

I have a ton of these to do and really don't understand them at all-

- Algebra II-Please help!! -
**Damon**, Monday, April 4, 2011 at 5:38pm
permutations:

That means all the arrangements of three made from the 12 when order is important. For example

ABC and ACB and BAC and BCA and CAB and CBA are all different.

The formula for that is

n!/[n-r]!

here n = 12 and r = 3

so we have

12!/9! which is 12*11*10 = 132

That is what you asked.

To answer what is coming next, combinations of n taken r at a time where order is NOT important are called indeed combinations and the formula is logically enough the permutation formula divided by r!

C(n,r) = n!/[ r! (n-r)! ]

- Algebra II-Please help!! -
**Anna**, Monday, April 4, 2011 at 5:54pm
Thank you for the explanation-it actually makes sense now

## Answer This Question

## Related Questions

- 9th grade algebra - I've never seen a problem like this, please help. I think we...
- Algebra II Please check- - Please help-What is the equation of the ellipse with ...
- Algebra II-Please check - Please help-What is the equation of the ellipse with ...
- Math - Find the probability that if the letters of the word "parallel" are ...
- HELP PLEASE - I'm really, really, really, sorry but I seriously need help. I can...
- algebra - using the letters in the word "MAGIC,", find the number of ...
- Dear Jiskha - Dear Jiskha, I really need help with some things and I am able to ...
- Math - What is the mathematical significance of time? I have calculus and E=Mc2 ...
- More Rational Exponents! - 1. The optimal height h of the letters of a message ...
- Math - To Reiny: Hi, thank you for your time Reiny and your info. I am so sorry ...

More Related Questions