Question

Out of ten different alphabates how many words with five letters are formed which have at least one letter repeated?

• A. 69670
• B. 69760
• C. 67960
• D. 67690

Answer 1

Answer: (B)

69760

Answer 2

Number of words when repetition is allowed = 10⁵

Number of words when repetition is not allowed = ${ } ^ { 10 } \mathbf { P } _ { 5 }$

∴ Number of words when at least one letter is repeated.

= 10⁵ -

= 100000 – 30240 = 69760.