Question

Ten different letters of an 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

• A. 69760
• B. 30240
• C. 99748
• D. None of these

Answer 1

The correct option is A 69760

Required number of words $=$ Total number of words - Total number of words in which no letter is repeated
$={10}^5{-}^{10}{P}_5$
$=1000000-10\times 9\times 8\times 7\times 6$
$=1000000-30240$
$=69760$