Question

how many eight-letter words can be constructed from the 26 letters of the alphabet if each word contains three, four or five vowels?

Answer 1

this can be solved by concept of permutation

total vowels=5

so among the eight letters in  the word 3 must be among these

and other letters can be any of the 26 letters

so ans is 5*5*5*26*26*26*26*26=5^3*26^5

hope its helpful