Ten different letters of alphabet are given, words with 5 letters are formed from these given letters. Then, the number of words which have at least one letter repeated is:

Answer: Option A

Number of words which have at least one letter replaced,
= Total number of words - total number of words in which no letter is repeated.
= 10⁵ – ¹⁶P₅
= 100000 − 30240
= 69760