Pluto should never be a planet because if we consider Pluto one than we would have 13 planets (or 14 if we consider Charon and Pluto binary dwarf planets which they really are) 5 (or 6 if charon is one) of which are smaller than earths moon and have not cleared their orbit
0/0=0 because if you have nothing and you split it into no groups there is nothing in any of the groups
Wikipedia is a great recourse
CYAN IS NOT BLUE THE TWO COLORS LOOK VERY DIFFERENT
I rarely use Wikipedia, since I prefer to use sources that I have used many times in the past, however it can be good for basic background information. I use it as a starting point, then find sources I trust more so. (Btw this is not to start an argument, I was simply stating what my opinion is, as it provoked some thought)