Question

# Ten different letters of an alphabets are given. Words with five letters are formed from these given letters. The number of words, which have at least one letter repeated is

A
59720
B
79260
C
69760
D
None of these

Solution

## The correct option is C $$69760$$Number of words when repetition is allowed is $$10\times 10\times 10\times 10\times 10 = 10^{5}$$.Number of words when repetition is not allowed is$$10\times 9\times 8\times 7\times 6 = 30240$$.Hence, required number of words in which at least one letter is repeated is $$10000 - 30240 = 69760$$.Maths

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