How many three letter words can be formed using `a , b , c , d , e` if Repetition is not allowed ii. repetition is allowed?

Explanation

(i) Total number of 3-letter words is equal to the number of ways of filling 3 places


First place can be filled in 5 ways by any of the given five letters
. Second place can be filled in 4 ways by any of the remaining 4 letters and the third place can be filled in 3 ways by any of the remaining 3 letters.


So, the required number of 3-letter words =`(5xx4xx3)=60.`



(ii) When repetition of letters is allowed, each place can be filled by any of the 5 letters in 5 ways.

...