Question 916353: imagine the alphabet only consisted of 7 letters abcdefg. If each letter can be use once. how many 4 letter words are possible?
Answer by Edwin McCravy(20055)   (Show Source):
You can put this solution on YOUR website! There are 7 ways to choose the 1st letter.
For each of the 7 ways to pick the first letter,
there are 6 ways left to choose the 2nd letter.
For each of the 7*6 ways to pick the first 2 letters,
there are 5 ways left to choose the 3rd letter,
For each of the 7*6*5 ways to pick the first 3 letters,
there are 4 ways left to choose the 4th letter.
In all, that's 7*6*5*4 = 7P4 = 840 ways.
Edwin
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