Where is it?

3 men go for dinner.
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Each buys a $10 steak. 
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At the end of the meal, they collect $30 between the three of them to cover the cost of the meal and give it to the waitress. 
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She goes back to the cash register, where the overlooking manager says. 
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"Those dinners are discounted, you need to give them $5 back." 
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So the waitress gets the five dollars, and returns to the table. 
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Not knowing how to split $5 between the three of them, she gives 1 dollar to each of the three patrons, and kept two for herself.
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Now if you do the maths.
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Together they paid $30.
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Received $3 back meaning they only paid $27. 
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The waitress kept $2. 
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This totals $29. 
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Where did the last dollar go?