Ten different letters of alphabet are given. Words with five letters are formed from these given letters.
Ten different letters of 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) 69760
(B) 30240
(C) 99748
(D) 99784
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(A) is correct choice. Number of 5 letters words (with the condition that a letter can be repeated) = 105. Again number of words using 5 different letters is 10P5. Therefore, required number of letters
= Total number of words – Total number of words in which no letter is repeated
= 105 – 10P5 = 69760.
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