Perplexing Donuts

A good friend and colleague, Krystal Shaw, tweeted this article about Krispy Kreme Donuts in the UK a while back and it immediately got me thinking. . . so I really liked it and wanted to use it with kids.  To plan for the lesson, I started to take myself through this problem as if it were a 3-act task (I wasn’t sure it would become one, but I wanted to see where this would lead).  I looked at the picture:

Top of Box

and jotted down what I noticed. Then I began wondering:

  • How many donuts are in that big box?
  • What are the dimensions of the box?
  • Is there more than one layer of donuts in the box?
  • How many rows of donuts are there?
  • How big is (What is the diameter of) a Krispy Kreme donut?
  • When I was finished (or thought I was finished) wondering, I began to seek the information needed to answer my questions.

I found some nice strategies for determining the number of donuts in the box.  Strategies accessible for 4th grade students.  I was happy, so I moved on to the next question: What are the dimensions of the box?

This is when it happened.

I was stuck.


Challenge accepted.

I looked at the pictures, found the information in the article, then began to question that information (and myself) as well as some critical friends.  This problem was getting better and better as I walked myself through it.  Fantastic!  SMP 3: Construct viable arguments and critique the reasoning of others, such as a Krispy Kreme representative from the UK or a USA Today reporter.  Maybe this question won’t have a third act, but the estimation and reasoning used to solve this could be extremely empowering for kids.

I challenge you to solve this problem with your class as well and share your results.     Challenge yourself and your students to construct a viable argument and critique the reasoning of others.  Does your math challenge the information in the article or support it.  Either way, integrate writing into math class in a meaningful way:

write to the reporter, Bruce Horovitz or Krispy Kreme UK: and tell them what you  discovered

Time for me to give this a try!  More in about a week.

By the way:  Krystal Shaw gave her amazing Mathletes after school club the task of writing a 3-act math lesson for their teachers to teach.  I think she should post it on her blog to share with the MTBoS!

Why use 3-Act Tasks?

The short answer:  It’s what’s best for kids!

If you want more, read on:

The need for students to make sense of problems can be addressed through tasks like these.  The challenge for teachers is, to quote Dan Meyer, “be less helpful.”  (To clarify, being less helpful means to first allow students to generate questions they have about the picture or video they see in the first act, then give them information as they ask for it in act 2.)  Less helpful does not mean give these tasks to students blindly, without support of any kind!

This entire process will likely cause some anxiety (for all).  When jumping into 3-Act tasks for the first (second, third, . . .) time, students may not generate the suggested question.  As a matter of fact, in this task about proportions and scale, students may ask many questions that are curious questions, but have nothing to do with the mathematics you want them to investigate.  One question might be “How is that ball moving by itself?”  It’s important to record these and all other questions generated by students.  This validates students’ ideas.  Over time, students will become accustomed to the routine of 3-act tasks and come to appreciate that there are certain kinds of mathematically answerable questions – most often related to quantity or measurement.

These kinds of tasks take time, practice and patience.  When presented with options to use problems like this with students, the easy thing for teachers to do is to set them aside for any number of “reasons.”  I’ve highlighted a few common “reasons” below with my commentary (in blue):

  • This will take too long.  I have a lot of content to cover.  (Teaching students to think and reason is embedded in mathematical content at all levels – how can you not take this time)
  • They need to be taught the skills first, then maybe I’ll try it.  (An important part of learning mathematics lies in productive struggle and learning to persevere [SMP 1].  What better way to discern what students know and are able to do than with a mathematical context [problem] that lets them show you, based on the knowledge they already have – prior to any new information. To quote John Van de Walle, “Believe in kids and they will, flat out, amaze you!”)
  • My students can’t do this.  (Remember, whether you think they can or they can’t, you’re right!)  (Also, this expectation of students persevering and solving problems is in every state’s standards – and was there even before common core!)
  • I’m giving up some control.  (Yes, and this is a bit scary.  You’re empowering students to think and take charge of their learning.  So, what can you do to make this less scary?  Do what we expect students to do:  
    • Persevere.  Keep trying these  and other open problems.  Take note of what’s working and focus on it!
    • Talk with a colleague (work with a partner).  Find that critical friend at school, another school, online. . .
    • Question (use #MTBoS on Twitter, or blogs, or Google 3-act tasks).  
    • Write a comment below. 🙂

The benefits of students learning to question, persevere, problem solve, and reason mathematically far outweigh any of the reasons (read excuses) above.  The time spent up front, teaching through tasks such as these and other open problems creates a huge pay-off later on.  However, it is important to note, that the problems themselves are worth nothing without teachers setting the expectation that students:  question, persevere, problem solve, and reason mathematically on a daily basis.  Expecting these from students, and facilitating the training of how to do this consistently and with fidelity is principal to success for both students and teachers.

Yes, all of this takes time.  For most of my classes, mid to late September (we start school at the beginning of August) is when students start to become comfortable with what problem solving really is.  It’s not word problems – mostly. It’s not the problem set you do after the skill practice in the textbook.  Problem solving is what you do when you don’t know what to do!  This is difficult to teach kids and it does take time.  But it is worth it!  More on this in a future blog!


One strategy I’ve found that really helps students generate questions is to allow them to talk to their peers about what they notice and wonder first (Act 1).  Students of all ages will be more likely to share once they have shared and tested their ideas with their peers.  This does take time.  As you do more of these types of problems, students will become familiar with the format and their comfort level may allow you to cut the amount of peer sharing time down before group sharing.

What do you do if they don’t generate the question suggested?  Well, there are several ways that this can be handled.  If students generate a similar question, use it.  Allowing students to struggle through their question and ask for information is one of the big ideas here.  Sometimes, students realize that they may need to solve a different problem before they can actually find what they want.  If students are way off, in their questions, teachers can direct students, carefully, by saying something like:  “You all have generated some interesting questions.  I’m not sure how many we can answer in this class.  Do you think there’s a question we could find that would allow us to use our knowledge of mathematics to find the answer to (insert quantity or measurement)?”  Or, if they are really struggling, you can, again carefully, say “You know, I gave this problem to a class last year (or class, period, etc) and they asked (insert something similar to the suggested question here).  What do you think about that?”  Be sure to allow students to share their thoughts.

After solving the main question, if there are other questions that have been generated by students, it’s important to allow students to investigate these as well.  Investigating these additional questions validates students’ ideas and questions and builds a trusting, collaborative learning relationship between students and the teacher.

Overall, we’re trying to help our students mathematize their world.  We’re best able to do that when we use situations that are relevant (no dog bandanas, please), engaging (create an intellectual need to know), and perplexing .  If we continue to use textbook type problems that are too helpful, uninteresting, and let’s face it, perplexing in all the wrong ways, we’re not doing what’s best for kids; we’re training them to not be curious, not think, and worst of all . . . dislike math.

More Resources like 3-Act Tasks: