Question

How many 5-letter code words are possible using the first 11 letters of the alphabet if adjacent letters cannot be the same?

Answer 1

11c5 wre c=combination

Answer 2

462 is ans

Answer 3

let the 5 coded word be denoted by -,-,-,-,-
the number of ways the first bar can be filled is 11, the second bar can be filled in 10 ways because one alphabet is already placed in the first bar, following the same reasoning, the third bar can be filled in 9 ways, the fourth bar in 8 ways and the last bar in 7 ways
therefor the answer is 11*10*9*8*7=55440

Answer 4

I'm rusty with this material - so may be wrong.

But,
It looks like we have 11 options to pick the letter in the first position.
For any of the 11 options we had for the first position, we now have only 10 options to pick from for the 2nd position (since we cannot repeat the same choice as in the 1st position).
For the 3rd position, we also have 10 choices to avoid repeating the same letter chosen for the 2nd position , etc.

So, for all 5 positions we should have something like:

11 * 10 * 10 * 10 * 10 = 111000

combinations of letters where no letter is the same as the letter in the previous position

Answer 5

there was a typo in my answer - it is 110000 (not 111000)