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Combination Question?
In how many ways can letters of the word BEHAVIOUR be arranged so that at most 2 vowels are together?
I considered 2 cases.
First case: All vowels are separated. I got 2880 ways.
Second case: 2 vowels are together. I cannot do it.
Please give me a clear explanation.
Thanks.
1 Answer
- ?Lv 74 years ago
V = vowel
C = consonant
1st case:
All vowels are separated: V C V C V C V C V
Only 1 such arrangement of V's and C's
5! ways to arrange the vowels
4! ways to arrange the consonants
5! * 4! = 2880
So that's ok
2nd case:
Think of the 2 vowels that are together as a single vowel.
So there are 4 "vowels" and 4 consonants, with no 2 "vowels" side by side:
V C V C V C V C
V C V C V C C V
V C V C C V C V
V C C V C V C V
C V C V C V C V
So there are 6 arrangements of V's and C's
There are 5*4 = 20 ways to pick the 2 vowels that are together
There are 4! ways to arrange the 4 "vowels"
There are 4! ways to arrange the 4 consonants
5 * 20 * 4! * 4! = 57600
Total number of arrangements = 2880 + 57600 = 60400