The Mystery of the Missing Dollar

December 9, 2015 | Elizabeth Knowles

3 men each pay $10 for their $30 hotel room. Realizing his error, the clerk later sends a poter to return $5. The porter gives the men each $1 but keeps $2. Each man has now paid 9 for a total of $27 and the porter has $2. 27+2= 29. Where is the rest?

Can you figure out where the extra dollar went?

Wait! Spoiler alert! If you think you’ve solve it and you want to check your answer, keep scrolling down. Otherwise, scroll up and give it one more try. I bet you can get it!

Need a hint? Think about exactly what you are adding and who has what money when. Why not try making a table?

Graph detailing where all the money went

If you look at row 1–4 individually, they all add up to $30. Everything makes sense. The confusing part of the problem lies in row 5—the total row. You need to consider the signs and what you are actually calculating. When you add what the guests paid and what the bellboy kept, there is no reason that it should add up to $30. The bellboy’s cut is included in what the guests paid. The wording of the question is just made to confuse you.

Still puzzled? Try thinking about it with different numbers. What if the hotel had wildly overcharged the guests and wanted to return $20 ($5 going to each of the guests and $5 going to the bellboy). The total of what the guests would end up paying would add up to $15, but would you still try adding $15 + $5 to get $30? No. That would be absurd!

Try this brain teaser next: Only 2% of People Can Solve Einstein’s Riddle

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