Three friends check into a hotel room that costs $30. They each contribute $10, handing $30 to the hotel clerk. Later the clerk realises the room only costs $25. He gives $5 to the bellboy to return. The bellboy keeps $2 and gives $1 to each guest. Now each guest has paid $9 (total $27) and the bellboy kept $2 — that’s $29. Where is the missing dollar?
There is no missing dollar. The guests paid $27: $25 for the room and $2 kept by the bellboy. Adding the $2 to $27 is the wrong operation; you should subtract it.
