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11 Math Problems That Look Simple But Are Not
written by Sam Greenspan

If Brain Teaser Tuesday was a thing, THIS would be great for Brain Teaser Tuesday. However, seeing as that is not a official thing (thanks for dragging your feet on that, OBAMA) -- these are just 11 math brain teasers for any old Tuesday.

If you saw this list title and didn't recoil in horror, prepare to have all sorts of nerd fun. If you saw this list title and did recoil in horror, there are approximately 600 other lists on this website that you'll probably want to check out. Click here to go to a random one. And also, welcome to Costco, I love you.

Because I respect you, I did not include the answers to these questions anywhere. However, at the end, if you want to add up the total of your answers and tweet it to me, I'll let you know if you're right or wrong. And if you include all of your answers (like 20 + 5 + 177 + etc...) then I'll let you know how many you're off.

(You can leave out the answer to the tennis problem, since there's really no way to add that in. So just send the sum total of the 10 problems, and you can include the tennis answer separately.)

Get to it.
  1. Racks on racks on racks of squares in squares in squares.

    How many squares are in this image?

    And no, the border around the image does not count. One, it's a non-square rectangle. And two, I'm not getting THAT tricky for problem number one.

  2. One-line equation #1.

    This is a nice, agreeable equation with a definitive right answer. It's here to ease you in to the other one-line equation later on this page that's a K12-esque widow maker.

  3. A tennis flash-in-the-pan (aka the Andy Roddick Dilemma).

    You have temporary magical powers that allow you to dominate the final at tennis's U.S. Open (in a five-set match). But the powers will wear off at some point in the match. What's the ideal score for the moment they wear off to give you the best shot at winning?

    And you don't have the option to just throw your opponent your mom's underhand softball pitch.

  4. Integer, eh?

    x is an integer and 9 < x2 < 99. What is the maximum value of x minus the minimum value of x?

    This one feels the most "math-y" of any problems on the list and is arguably the only one that is probably appearing on some kids' math tests somewhere in the world today. And for that, I apologize. High school never ends.

  5. That's a whole lot of cats.

    As crudely illustrated above, there are seven sisters standing around the kitchen table. Each one has seven backpacks. In each backpack, there are seven large cats. For every large cat, there are seven small cats. How many legs are there in the room?

    Get this right and you'll get a scholarship to the Seven Sisters college of your choice. And a hot plate!

  6. The 11 sequence.

    What are the next two numbers in this sequence?

    I had to find at least one problem with an "11" in it. Even though -- potentially confounding hint -- this isn't as much of an 11 as you might initially think.

  7. Yous guys want to play stickball?

    If a baseball and bat cost $110, and the bat costs $100 more than the ball, how much does the ball cost?

    This problem is so old that I remember doing it once upon a time where the bat and ball cost $1.10. The prices really have soared. Occupy Sports Authority.

  8. The 3, 76, 49, 24, 59, 36 sequence problem.

    What is the next number in this sequence?

    This is either the hardest or easiest one on the list. If you're reading this and not already on to the next question, then for you, it's the hardest.

  9. Balls in the balance.

    There are nine balls. One is slightly lighter than the rest; the difference is small enough that you can't tell just by picking them up. Using a basic two-sided scale, what's the minimum number of times you'd need to weigh balls to guarantee you find the light one?

    This is one of those questions that, allegedly, gets asked in job interviews. I say "allegedly" because I don't really believe places really give brain teasers. (Although I haven't had a job interview since 2003, so maybe they've changed, man.)

  10. Fancy foreign math.

    In a foreign country, half of 5 = 3. Based on that same proportion, what's one-third of 10?

    For some reason, when I found this question, it inexplicably made me think the foreign country is a former Soviet republic. Kyrgyzstan? Azerbaijan? Moldova? It's Moldova, isn't it?

  11. One-line equation #2.

    If you're like me, this will open up a rabbit hole where you learn all about the concept of implied multiplication precedence. You'll start missing work and family events because you get so deep, only to emerge on the other side just as uncertain as you were when you entered. The hero's journey isn't always a happy one.

This list was originally published on Tuesday, March 5, 2013 at 11:00:00 AM under the category Misc.
It currently has View Comments.

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