SOLUTION: How many distinct permutations of 4 letters from EAGLES are there? I first tried to do cases. My first case was to leave out all the non-repeated letters so I ended up with

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Question 1191631: How many distinct permutations of 4 letters from EAGLES are there?
I first tried to do cases.
My first case was to leave out all the non-repeated letters so I ended up with 4•4!/(2!) = 48
My second case was to leave out all repeated letters and ended up with 1•4!/(1!) = 24
When I add them, it equals up to uw permutations but my answer key says 192 permutations. Please help me find where I went wrong with this question! Thanks!

Answer by ikleyn(52778)   (Show Source): You can put this solution on YOUR website!
.

The word EAGLES has 6 letters; of them, one letter E is repeated and have a multiplicity 2.

When we analyze the number of different words of 4 letters formed from the given word (symbols),
we should distinct two different cases.


Case 1.  All 4 letters in the final word are different.

         In this case, we have only 5 distinct letters to choose from, (E, A, G, L S);

         therefore, the number of possible words to form is  5*4*3*2 = 120  in this case  (the order of letters does matter !);



Case 2.  In the final word, we have 2 identical letters E and any 2 of the remaining 4 letters.

         In this case, we can select these two remaining letters by   = 6 different ways,

         and we can arrange then 4 letters with two repeating undistinguishable Es by  

              =  = 12 different distinguishable ways.


         Combining everything altogether, we have 6*12 = 72 different words in Case 2.



Cases (1) and (2) are the disjoint sets of words; therefore, the answer to the problem's question is 120 + 72 = 192.


ANSWER.  192 different / (distinguished) words of the length 4 can be formed.

Solved.



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