1) I assume you are asking how many distinct 4 letter words can be formed. Change the problem by forcing an N and making the problem, How many distinct 3 letter words can be formed?
2) The number of 3 letter words that can be formed from COMBINATIO (no final N) is 10 pick 3 distinct (i.e. 10P3) corrected for the repeated letters as they can change places and not form new words
10P3/(2!2!) If they hadn't said that it has to have an N, the answer would have been 11P4/(2!2!2!)
Louis M.
Like for 2 alike, 2 alike There are 3 pairs of 2 letters. So, the number of ways of selection of 2 pairs is 3 C 2 and permutation of these 4 letters is 2!2!/ 4! Therefore, the number of words in this case is 3 C 2 × 2!2!/ 4! =18.
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05/15/22
JACQUES D.
tutor
Sorry.I don't understand the problem.
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05/16/22
Louis M.
You This is actually a 'combination' nCr question, instead of nPr, because the question is asking about the number of ways the letter is selected.. There are 11 letters in the word COMBINATION I think there are 3 pairs of alike (2 N, 2 O, 2 I), the number of ways of selection is reduced to 8. Since N must be selected, for the selection of 4 letters we have the following possibilities: (A) 2 alike, 2 alike (B) 2 alike, 2 different (C) All four different But I still need someone help to sort out a bit of concept - based on expert's point of view. Kindly help05/15/22