Question

Words of $4$ letters are to be formed from $10$ different letters. How many words are formed in which at least one letter is repeated?

• A. $10240$
• B. $2440$
• C. $6970$
• D. $4960$

Answer 1

The correct option is D $4960$

Four letter words can be made by $10$ letters in ${10}^4=10000$ ways

Total number of $4$ lettered words with no repetition

${}^{10}{C}_4\times 4!=5040$

$=4960$