SOLUTION: A security system uses a 6-letter password, but no letter can be used more than once. How many possible passwords are there if 18 of the letters of the alphabet can be used by the

Question 880246: A security system uses a 6-letter password, but no letter can be used more than once. How many possible passwords are there if 18 of the letters of the alphabet can be used by the system? I am using the formula: Permutation w/ N= 18 and r = 6. Is that correct?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
Re TY
no letter can be used more than once...(order Important)...does
fit the picture of 18P6 = 18!/12! =
Common sense approach is 18 choices for 1st letter AND 17 choices for the 2nd letter etc

As one embarks into the topic of statistics...albeit, it is not necessary to
"re-invent the wheel" so to speak and Yes, there are procedures and formulas
that 'work' in most cases...best sometimes to look at 'why they may work'
for a particular scenario, as in this example... As some situations do not
lend themselves to a particular robotic way of looking at things.
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