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osanseviero
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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)
 one year ago
 one year 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)
 one year ago
 one year ago

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Easyaspi314 Group TitleBest ResponseYou've already chosen the best response.0
a) thats a combination of 3 from 5..or 5 C 3
 one year 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)?
 one year 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 \(5C3\)
 one year ago

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

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

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

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

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

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

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

osanseviero Group TitleBest ResponseYou've already chosen the best response.0
So it is 125 and 10 :)
 one year ago
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