The total letter arrangements for the word GRACEFUL is 8!
.
The question is: What fraction of all arrangements of GRACEFUL
have no pair of consecutive vowels?
Now the three vowels in this word are A
, E
, and U
. They can appear consecutively in 3P3
ways so this can be handled in 8! / 3P3
ways. But it is also possible that any two can appear consecutively.
So would the answer be: 8! / (3P3) * 2! * 3
?
Best Answer
Since there cannot be consecutive vowels, remove two consonants (we'll add them back in shortly). We can look at the number of ways to arrange $3$ vowels and $3$ consonants, now without the restriction on consecutive vowels. There are $6\choose3$ ways to do this. For any arrangement, add one consonant between the first and second vowel, and another between the second and third.
Now assign vowels and consonants: there are $(3!)(5!)$ ways to do this. The fraction you are looking for is therefore: $$\frac{{6\choose3}(3!)(5!)}{8!}$$