Three friends go to a bar for drinks.
They order a bottle of champagne from the assistant who brings it to them and charges $30.
They each pay him $10.
When the owner of the bar returns, the assistant tells him he didn’t know how much to charge for the champagne (a brand they hardly ever sell) and that he has charged them $30.
The owner says this is too much – it should have cost $25 and tells him to give them $5 back.
The assistant takes 5 one dollar coins from the till and realizing he can’t divide the $5 evenly among three people gives each person $1 back and puts the other $2 in his pocket.
Now, each person paid $9 for their share of the champagne 3 x $9 = $27 plus the $2 the assistant put in his pocket makes $29.
Where is the missing dollar?