In Canada, the one dollar coin is called a loonie because it has the loon bird on it. Hence, the title I gave to this common riddle that you can Google to find explanations for that range from simple to complex.
Three men go to lunch at a restaurant. The total comes to $30, so each man pays $10. The manager realizes the bill should only be $25, so he asks the waiter to return $5 to the men. Each man takes back $1, and they tell the waiter to keep the remaining $2 as a tip.
Each man now has $1 back in his pocket, meaning they each paid $9 for the meal. That comes to a total of $27. The waiter has $2 as a tip. If the men originally handing over $30, what happened to the missing dollar?