Permutations and Combinations (1 Viewer)

[faisalabdul16]

A nine letter arrangement consists of 3 A's, 3 B's and 3 C's such that there are:
- no A's in the first three letters
- no B's in the next three letters
- no C's in the last three letters

i) Find the number of nine letter arrangements if the first three letters are 2 B's and 1 C in some order.

 

[Axio]

I get 27

1st: 2B 1C, no As
2nd: no Bs, 2C 1A
3rd: no Cs, 2A 1B

1st: BBC, BCB, CBB = 3

Same patterns with 2nd and 3rd so:
3x3x3 = 27

 

[Axio]

Braintic for your (I) aren't no Bs allowed in middle?

 

[braintic]

Yep. I will just give up now.