Horse Algebra Goes Viral!

When a math problem goes completely viral on the internet…I sit up and pay attention. This is an absolutely amazing problem to spark a math discussion in  your class. It looks deceptively simple. Let me tell you something…it isn’t! Don’t get overconfident! Take your time and give it a shot right now!

 

brainteaser-algebra-question

Do you have an answer???

There is an incredibly HUGE chance that you are WRONG…even if you are supremely confident!!

Thousands…literally THOUSANDS of people across the world have been baffled by this simple problem. I’m not talking about just the general population either…I’m talking about MATH TEACHERS, too!!

It’s an example of a super fun way to spark a spirited debate and discussion about math. As people try to justify their answers it leads down wonderful paths to explore.

If you like this way of thinking…taking viral stories and issues from the world around you and using them in class, you are going to absolutely LOVE Instant Relevance by Denis Sheeran (to be clear, the above example is not from the book)! It is our latest book release and it is not only hilarious, but also filled with practical ways to make learning fun and relevant. Many, but not all, of the examples are from math classrooms. It is much more about a mindset, though, as opposed to the math. Always ask, “How can I use that?”

This could be a great way to spark a conversation at the dinner table, too! In fact, that is exactly what we did last night and the results were unbelievable! Total engagement. Total fun. AND…it was all about math!! For more examples of bringing math home in a fun way, check out this TABLE TALK MATH post.

Wait!!! Are you still reading down here because you want to check your answer????

Where would the fun be in that!! If I just let you scroll down and get the answer it takes you off the hook. The fun is in the journey!

But…I will reiterate…YOU ARE PROBABLY WRONG! Don’t look up the answer to this until you have shown it to at least 5 different people (or all of your classes) and you have seen for yourself how outrageously different the answers will be.

It is INSANE!!

Okay…if you get really desperate to know you can beg in the comment section or hit me up on Twitter at @burgessdave.

Remember! This is a problem to be shared and discussed! Some things are WAY more fun when done with others. (Hey! Relax! I’m talking about MATH!)

Let me know how it goes!

Dave

Please note: I reserve the right to delete comments that are offensive or off-topic.

69 thoughts on “Horse Algebra Goes Viral!

  1. I’ve GOT to know the answer!
    Is it 42???? Inquiring minds want to know (as well as a Math teacher who lives in my house).

  2. Hi Dave, I’m Janet Jury (I actually introduced you when you presented in Syracuse NY last Spring). I’m begging you to HELP me with this. I teach an amazing group of gifted New Visions students at our local BOCES and I love it when I can stump them, especially early on in the school year. On a side note, I read two more of the books you recommended over the summer and LOVED them both. Thank you for helping make teaching so FUN. Oh, one more thing, I loved the branches of government (rope) lesson you shared with us, is that written down anywhere so I can steal it?

  3. Hi Dave,

    We just tackled this problem in my 2nd hour math class and we are CONVINCED!!! … that the answer is 21! Boom!

    Mr. Kosal – Wheeler High School

  4. The answer is 21 because on the last line you have to follow PEMDAS. On the last line, you do multiplication first and the addition.

    Right?

  5. OK. I think that I have the answer and have several others from friends. Will you please send the correct answer so we can end the discussion on whose answer is the “right” one?

  6. h+h+h=30

    h+u^2+u^2=18
    or
    h+uu+uu=18
    or
    h+(u×u)+(u×u)=18

    u^2-b^2=2
    or
    uu-bb=2
    or
    (u×u)-(b×b)=2

    b+(h×u)=21.4142135624

    Someone correct me if I am wrong here “(t)he symbol (⋅), (×), or (∗) between two mathematical expressions, denoting multiplication of the second expression by the first. In certain algebraic notations the sign is suppressed and multiplication is indicated by immediate juxtaposition or contiguity, as in ab.”thus two horse shoes or two boots would not simply be added together but multiplied.

    • Hi, Maurice! You are going deep! My answer differs…but, never trust a history teacher on a math problem!

      • Mr. Burgess,
        It is my understanding that the most common answer would be 21, then you have my irrational number answer which of course I believe to be correct, there is a rational number answer that differs from mine and is not 21 that rationalized the second images are all exponents…

        I never found much joy in math until later in life where I found a practical use for it in a hobby, and again when my children needed help with their own schoolwork.

        This problem certainly sparked some renewed interest in working with numbers amongst my own circle of friends.

        Thank you,
        Maurice

  7. 13
    I’m going to be at your conference at Tan-Tar-A this month. I’m super excited! 🙂
    I came to your page to read some information about the conference and saw this problem. I’m a math teacher and of course had to try to figure it out! 🙂

  8. I am so excited to do this one with my class. Just staring equations with my 7th graders and we have been stressing discourse and critical thinking. I LOVE that you aren’t giving the answer. We need to learn to be ok with that and teach our kids that it isn’t about the answer but the effort and discourse! Thanks.

  9. If horse equals 10, 2 boots equals 2, then 1 boot equals one. A pair of horseshoes equals four. So 1 boot equals 1, 1 horse equals 10 so (1 + 10) X 2 = 22

  10. Symbols serve the same function as variables in an algebra problem. This is a series of 1- and 2- step algebra equations. 1 horse has a value of 10. One horseshoe has a value of 2. One boot has a value of 1. Insert these values into the last equation, apply the order of operations correctly, and we get 21.

    Right?

  11. h+h+h=30
    h+s+s=18
    s-b=2
    b+h x s=d 1/2
    =
    10+10+10=30
    10+s+s=18
    s-b=2
    b+10 x s=d 1/2
    a=10
    =
    10+10+10=30
    10+4+4=18
    4-b=2
    b+10 x 4=d 1/2
    b=4
    =
    10+10+10=30
    10+4+4=18
    4-2=2
    2 + 10 x 4=d 1/2
    b=2
    =
    horse=10, shoe=4, boot=2, 1 boot=1, 1 shoe=2,
    2 +10 x 4= (4×10)+2=40+2=42 ½= 21

  12. It’s clear that horse=10, boot=1 and shoe=2. So depending on the sequence of operations in the last equation, the answer is either 12 or 22. I haven’t taken math for awhile, so don’t know the current rules. I would expect to be guided by parentheses.

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