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SOMEONE HELP ME PLEASE

Decide if the following scenario involves a permutation or combination. Then find the number of possibilities.

You are setting the combination on a five-digit lock. You want to use the numbers 12345 but you don't care what order they are in.

User ChrisZZ
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1 Answer

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Answer:

It's a combination, BUT...

Explanation:

Definition: A combination is a grouping of outcomes in which the order does not matter. That's the difference between combination and permutation.

Combination Formula: nCr = (n!)/[r!(n-r)!)] where n stands for number of things and r the pair chosen

Applied to this case: We have n=5 (12345) and r=5 for the 5-digit lock combination.

5C5 = (5!)/[5!(5-5)] = 1

But!! As you can see, we cannot have 1 possible combinations so.. We have to assume that this is a permutation!!! Conceptually, this looks pretty much like a combination, but being the same range as number of items, we conclude that it's a permutation.

Permutation Formula: nPr = (n!)/(n-r)!

nPr = (5!)/(5-5)! = 120

Well, this looks way more accurate now, right?

Final Answer: The scenario involves a permutation, and there's 120 possible combinations of those 5 numbers in a 5-digit lock.

User Renra
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