More Frustrating Math Riddles – IOTW Report

More Frustrating Math Riddles

Since this one was more difficult than I thought it would be, this one might bend some minds.

Three guests check into a hotel room. The manager says the bill is $30, so each guest pays $10. Later the manager realizes the bill should only have been $25. To rectify this, he gives the bellhop $5 as five one-dollar bills to return to the guests.

On the way to the guests’ room to refund the money, the bellhop realizes that he cannot equally divide the five one-dollar bills among the three guests. As the guests are not aware of the total of the revised bill, the bellhop decides to just give each guest $1 back and keep $2 as a tip for himself and proceeds to do so.

As each guest got $1 back, each guest only paid $9, bringing the total paid to $27. The bellhop kept $2, which, when added to the $27, comes to $29. So, if the guests originally handed over $30, what happened to the remaining $1?

48 Comments on More Frustrating Math Riddles

  1. I gave away 30 dollars in iOTW bucks, giving each reader 10 bucks, but realized I was only supposed to give twenty-five. Each reader got ten. Now I need five back. They each gave me a dollar, leaving 9 each, which is twenty-seven, and said they would donate 2 to Trump. How many potatoes do I now have?

  2. The bellhop should never have bothered to return any of the $5, it was guaranteed to cause problems – whether an argument about how much each should have gotten back, or about how to do the math! Silly bellhop! 🙂

  3. Here’s another good one.

    You have a solid sphere, and you drill a hole all the way through it, dead center. The hole is six inches long. What is the volume of the material left in the sphere, i.e., what’s left after you drilled the hole?

  4. I’ve watched a swindler use this technique to confuse a cashier in order to steal a few bucks from her back in 1979. I was a stock clerk still in high school. After he left the store she called the manager once she realized she was duped. The manager got her to explain what she remembered and they tried to re-enact the exchange and after a few minutes gave up. They never really were able to determine how much he stole.
    It’s sad that people will put this much effort into an illegal activity rather than actually performing real work for a fair pay.

  5. @Jethro — I’ve only ever known one man who went in for this sort of petty con job stealing. He didn’t do it for the money, he did it because it entertained him.

    Not my kind of amusement, I have to say.

  6. Jethro, people these days cannot do simple math in their head.
    Ironically they call it “equity.”

    I paid a guy $20 for a $17 fee, he picked up his phone to calculate the $3 change.
    He was in his early 20’s
    I literally shook my damn head!

  7. When I was 16 the first thing the store manager taught me was what bins to put the money into in the till. The next thing she taught me was how to count up change.
    After that she told me to always rest the money the customer gave me on the shelf just above the till and not to put it into the till until the customer was satisfied with the change in case there was a dispute.
    Also – when the bins get full move the extra bills down into the little safe below the register.

  8. Fur, I turned your potatoes into french fries and they got stale before the mail got them to you, so you threw them out to the birds, who got sick and waited for you to come out and pooed all over you.

    Now, aren’t you sorry you asked???

    I hate math!

  9. “As each guest got $1 back, each guest only paid $9, bringing the total paid to $27.”


    Correct cost per guest is $25 / 3 = $8.33

    Actual cost per guest is ($30 – $2) / 3 = $9.33

    Assuming that each guest only paid $9 introduces a rounding error.

  10. @ Jethro Wednesday, 22 May 2024, 18:22 at 6:22 pm,
    Do you remember when Cashiers could count back your change from the charge to the payment? As opposed to counting out what the machine states is the change. I don’t think I’ve ever handed over payment without knowing what change to expect…

  11. 36π in³

    The key concept is that the six inch HEIGHT of the hole is the constant and the diameter of the sphere will vary with the DIAMETER of the hole. The wider the hole, the thinner the ring of remaining material. It turns out that it’s all the same answer as if you drilled a hole of zero width, then you can simply use the formula for the volume of a sphere.

  12. @General, that Depend®s on the curvature of the saddle and just how hyperbolic you want to be in describing the smell, and then there’s Ӫ to consider, the ratio of dingleberry radius to separation.

    But to answer your question, I have to say that calculating it is at the very top of my list of things to put at the very bottom of my to-do list! 😎

  13. Amazing, Uncle Al. Butt I guess for years, I had Ӫ wrong (theta double dot for non-engineers). I thought it was the angular acceleration of a shit load trapped in his pants as he spun around to avoid a slap by a girl’s mother. But you know, the ratio of dingleberry radius to separation does make a lotta sense. Empirical evidences suggests that his dingleberry radius can get alarmingly large.

  14. First grader version:

    “I have eleven fingers.” (Hold up one hand to count fingers) “Look: 10, 9, 8, 7, 6…” (hold up other hand) “and five, is eleven.”


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