Missing dollar riddle; Maths Group Tuition 2014

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Maths can be fun too!
Build up interest in Mathematics by trying out some of these interesting Maths Riddles.

Source: http://en.wikipedia.org/wiki/Missing_dollar_riddle

The riddle

Three guests check into a hotel room. The clerk says the bill is $30, so each guest pays $10. Later the clerk realizes the bill should only be $25. To rectify this, he gives the bellhop $5 to return to the guests. On the way to the room, the bellhop realizes that he cannot divide the money equally. As the guests didn’t know the total of the revised bill, the bellhop decides to just give each guest $1 and keep $2 for himself. Each guest got $1 back: so now each guest only paid $9; bringing the total paid to $27. The bellhop has $2. And $27 + $2 = $29 so, if the guests originally handed over $30, what happened to the remaining $1?

Try it out before looking at the answer!