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 are
(a) 69760
(b) 30240
(c) 99748
(d) none of these

Answer 1

Its (b). As

Permutation of 10 words taken 5 at a time = 10!/(10-5)! = 10*9*8*7*6 = 30240