Question

10 different letters of English alphabet are given. Out of these letters, words of 5 letters are formed. How many words are formed when at least one letter is repeated

• A. 99748
• B. 98748
• C. 96747
• D. 97147

Answer 1

Answer: (A)

99748

Answer 2

Number of words of 5 letters in which letters have been repeated any times = $10^{5}$

But number of words on taking 5 different letters out of 10 = $10C_{5} = 252$

$\therefore$ Required number of words = $10^{5} - 252$ = 99748.