Ten different letters of an alphabet are given. Words with five letters are formed from these given letters. Then the number of words which have atleast one letter repeated, is

Ten different letters of an alphabet are given. Words w... | Permutations and Combinations (Mathematics)

The number of 5 letter words with atleast one letter is repeated

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Total number of 5 letter words - Number of 5 letter words with all different letters

\\= 10^{5} - \ ^{10}P_{5} = 69760