Box of Secrecy
A group of girls (at least two) wanted to know the average age of the entire group but none of them are willing to divulge their age. They devised a strategy by using a calculator that doesn't store steps such that each girl tapped some keys and passed it on to the other girls. After some finite time, they had the average of their ages but no one knows the exact age of any other girls.
If the total number of girls is 99, how many possible number of girls are there such that they can accomplish this task?