medal!
How many combinations of a president, vice-president, secretary, and treasurer can be chosen from a group of 12 students?
11,880
95,040
665,280
3,991,680
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OpenStudy (luigi0210):
This is permutations correct?
OpenStudy (anonymous):
yesss
OpenStudy (anonymous):
@Luigi0210
OpenStudy (luigi0210):
Do you know the formula for permutations?
OpenStudy (anonymous):
yes nPr+ n!/ (n-2)
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OpenStudy (luigi0210):
Just plug in values :)
OpenStudy (anonymous):
but the answer...we dont have this option
OpenStudy (anonymous):
!
OpenStudy (luigi0210):
Wait, nvm it's a combination!
OpenStudy (anonymous):
please just help me
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OpenStudy (anonymous):
@Luigi0210
OpenStudy (dape):
Think of the different positions as 4 seats. For the first seat we can choose from 12 students, for the second we have 11 students left to choose from, continuing we get:
\[ 12\times11\times10\times9=11880 \]
OpenStudy (dape):
This can also be written as
\[ \frac{12!}{(12-4)!} \]
Which hints at the general formula for permutations
\[ \frac{n!}{(n-k)!} \]
Where \(n\) is the number of choices have for each "seat" and \(k\) is the number of "seats".