Since the order matters Person A and B can be chosen as AB (A pres B vice pres) or BA (B president A Vice president)
When the order matters we are talking about permutations. How many permutations of 11 taken 2 at a time are there. It can be written like this 11nPr 2 It means start at 11 and multiply by the next lower number 11 x 10 = 110 ways they can choose. Extension of the concept: If there had been three positions President, Vice President, and Treasurer then it would be 11nPr3 or 11 x 10 x 9 Once again the answer to your problem is 110.
