Q. 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
A) 69760
B) 30240
C) 99748
D) None of these
Explanation
(a)
The total number of ways in which words with five letters are formed from given 10 letters $= 10^{5} = 100000$
Total number of ways in which words with five letters are formed (no repetition) $= 10 \times 9 \times 8 \times 7 \times 6 = 30240$
$\therefore$ Required number of ways $= 100000 - 30240 = 69760$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.