Answer with Step-by-step explanation:
We are given that A,B,C,D,E and F.
We have to find the number of different four -letter arrangements can be formed using given six letters a,if the first letter must be C and one of the other letters must be B and no letter can be used more than once in the arrangement.
Number of letters=6
We have to arrange four letter out of six
After fixing C and B then we choose only two letters out of remaining four letters and repetition is not allowed.
Permutation formula :
We have n=4 an r=2
Using this formula and substitute the values
Then, we get
Hence, number of different four -letter arrangements can be formed using six letters when repetition is not allowed=12