Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
osanseviero
Group Title
If I have 5 letters (A,B,C,D,E), and I want to form groups of three letters.
a) How many can I form? (AAA, AAB, AAC, etc)
b) How many without repeating? (ABC, ABD, etc)
 9 months ago
 9 months ago
osanseviero Group Title
If I have 5 letters (A,B,C,D,E), and I want to form groups of three letters. a) How many can I form? (AAA, AAB, AAC, etc) b) How many without repeating? (ABC, ABD, etc)
 9 months ago
 9 months ago

This Question is Closed

Easyaspi314 Group TitleBest ResponseYou've already chosen the best response.0
a) thats a combination of 3 from 5..or 5 C 3
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
So 125 in the first one, and 20 in the second one. Why is it n(n1)?
 9 months ago

Hero Group TitleBest ResponseYou've already chosen the best response.1
If I'm not mistaken the first one is a permutation since elements are allowed to repeat. Which means the total number of three letter formations should be \(n^r=5^3 = 125\) The second question is a combination since elements are not allowed to repeat. So I imagine that it is \(5C3\)
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
Ok, let me check :)
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
I searched an in a permutation elements cant be repeated :/
 9 months ago

Hero Group TitleBest ResponseYou've already chosen the best response.1
You should do more research on permutations.
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
So the basic formulas are \[n ^{r}\] if they can be repeated and NCr, when they cant be repeated?
 9 months ago

Hero Group TitleBest ResponseYou've already chosen the best response.1
This resource might help clear things up a bit more: http://www.mathsisfun.com/combinatorics/combinationspermutations.html
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
Thanks :)
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
Yep, this helped me a lot :)
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
I am seeing that the formula of the combinations without repetition and permutation without repetition are the same. How can I know if this if a permutation or a combination? (the order matters here?)
 9 months ago

Hero Group TitleBest ResponseYou've already chosen the best response.1
They're not the same :)
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
oops, not the same, I reduce by r one more time. But how can I know in this case if it is permutation or combination?
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
(from the question?, how can I know if order matters?
 9 months ago

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
So it is 125 and 10 :)
 9 months ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.