-The Gringott's goblins' return the muggle money they they acquire back into circulation.
-The approximate value of a Galleon is about five pounds ($7.30 or 8.00 Euro), though the exchange rate varies.
-Dumbledore is 150, McGonagall is 70 (and is really an old softy, just doesn't act like it), Snape is 35 or 36.
-The happiest people do not become ghosts (therefore we can take it that ghosts are people that died while sad, angry, etc. Myrtle was teased, Nearly Headless Nick didn't have his head completely chopped off, the Bloody Baron was...lonely?)
-The Hogwarts teachers do not stay at Hogwarts during the Christmas holidays. Filch, Hagrid and Dumbledore do.
-To remove Dudley's tail that Hagrid gave him in the hut on the rock the Dursleys went to a private hospital where the staff was very discreet, and said that a wart had got out of control.
-Aragog is an Acromantula (see "Fantastic Beasts and Where to Find Them")
-Azkaban is in a sea north of the North Sea. A very cold sea.
-You can do unfocused and uncontrolled magic without a wand (like when Harry blows up Aunt Marge), but to do really good spells you need a wand.
