JEE AdvancedPermutation and CombinationHardBloom L3
Question
Ten different letters of an alphabet are given. Words with five letters are formed from these given letters. Then, the number of words which have at least one letter repeated, is
Options
A.69760
B.99748
C.30240
D.None of these
Solution
Total number of five letters words formed from ten different l
letters = 10 × 10 × 10 × 10 × 10 = 105
Number of letters words having no repetition = 10 × 9 × 8 × 7 × 6 = 30240
∴ Number of words have at least one letter repeated
= 105 - 30240 = 69760
letters = 10 × 10 × 10 × 10 × 10 = 105
Number of letters words having no repetition = 10 × 9 × 8 × 7 × 6 = 30240
∴ Number of words have at least one letter repeated
= 105 - 30240 = 69760
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