Question

Ten different letters of English 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

• A. $30240$
• B. $69760$
• C. $99748$
• D. None of the above

Answer 1

The correct option is B $69760$

Number of words with no restriction $=(10{)}^5=100000$

and the number of words in which No letter repeated
$=10\cdot 9\cdot 8\cdot 7\cdot 6=30240$

Thus, the number of words which have at least one repeated letter
$=100000-30240=69760$