#ExploreMTBoS Task 1 – Favourite rich task.

Screen Shot 2013-09-14 at 7.39.21 PMThis community is so badass that we have a group of teachers who have given up a bunch of there time just to get more people involved. I’m helping by doing what they ask me to do. So here’s my blog post for mission one:

Mission #1: The Power of The Blog

“What is one of your favorite open-ended/rich problems? How do you use it in your classroom? (If you have a problem you have been wanting to try, but haven’t had the courage or opportunity to try it out yet, write about how you would or will use the problem in your classroom.)”

Since I’m a maverick, and I can’t possibly choose a favourite, I’m going to write about a couple of tasks…


My New Patio – Nrich


Why I love it

Because it’s easy to explain to students. The entry point is so low. ‘Draw a square on your squared paper. Shade in one small square. Now fill the other space with more squares’. I love that the task lends itself to asking easy questions with hard answers.

Generic questions I like to ask:

  • What’s the most tiles needed? Why?
  • Can you write a rule for this?
  • What’s the fewest tiles needed?
  • Can you tell me a rule for this?
  • OK, that was a really hard question; can you tell me a rule for [subset of squares]
  • Are you sure that’s the best you can do?

Stuff to think about

This task benefits greatly from systematic thought and layout; recording strategies and group co-ordination. Is there any point in everyone working on the same size square? Is it a good idea to have everyone working on different sizes?

The ceiling on this task is pretty high. For one subset of squares you can prove that a certain type of tiling is always possible by induction. I’m not sure if there is a rule; every time I have done this task a student has come up with a way to foil any rule his/her peers could come up with. This might put some folks off; but how nice is it that a task that seems so easy can be so hard?? The one problem I have with this task is that it is difficult to link the task itself to specific curriculum points. But if that doesn’t matter to you; or you feel the Problem Solving Skills aspect is all it needs (as I do, sometimes…) Then crack on.

And if you find an answer; with a PROOF; let me know!

Pent/Hex/Polyominoes and Nets

I’ve used this task in many ways. I’m grouping it all together under one heading but I’ve done:

  • Systematic finding and classifying of Pent/Hex/Polyominoes
  • Arranging and tiling with Pent/Hex/Polyominoes
  • Linking to nets of shapes, including other platonic solids

Why I love it

The low entry point for finding the different pentominoes means it can be explained quickly for learners of all abilities. The fact that they benefit from working systematically is great and the discussion over what defines ‘sameness’ and ‘different’ is hugely valuable; particularly if you are going to be studying congruence. The nets of cubes extension to hexominoes builds spacial reasoning and awareness. Getting learners to try to find tilings of rectangles with the pentominoes gets them working on a problem that puzzled recreational mathematicians (the horror on some students faces when they discovered that those exist!) for decades.

Questions I like to ask

  • Are you sure you have got them ALL
  • Compare with student X; they say they’ve found [number] more than you
  • Are these the same?
  • What makes them different?

Stuff to think about

This can take a LONG time. Make a decision beforehand as to whether you count reflections/rotations as ‘the same’. Think carefully about this; when rotations and reflections are not considered to be distinct shapes, there are 35 different free hexominoes. When reflections are considered distinct, there are 60 one-sided hexominoes. When rotations are also considered distinct, there are 216 fixed hexominoes. So be prepared for students to find hundreds if you allow rotations. Students trying to visualise whether their polyomino makes a net will probably ask for scissors to test it out physically. I always say yes; but be prepared for this.

Also be aware that conjectures come easily in this task, but proofs are few and far between; and VERY challenging. Maybe because of this, like the task above, curriculum links can be challenging. So go for Problem Solving Skills instead πŸ˜€

My (possible) New Favourite – Des-Man


I haven’t used it yet. But it looks awesome. This could easily become my favourite rich task. The step by step intro lowers the entry point and the fact students can use ANY function puts the ceiling WAAAAY up there. If you are starting transformations of functions, linear graphs, conics, anything involving a function in any way I suggest looking at this.


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8 Responses to #ExploreMTBoS Task 1 – Favourite rich task.

  1. Mr. Chase says:

    Love this, Nik. Thanks for sharing!

    I’m a huge fan of “easy questions with hard answers” and I think this is the hallmark of great, interesting mathematics. Probability/combinatorics questions are often this way, like “How many ways can you color the sides of a cube with three paint colors?” (not a good one for high school students!)

    The fact that there’s not an obvious answer here doesn’t necessarily detract from the task. Like you said, the ceiling is high–perhaps infinitely high! So that makes it interesting for every student automatically.

    • nik_d_maths says:

      Thanks Mr C.

      My favourite moment from this was the second time I did it, and I had in my mind the ‘rule’ from the previous attempt. And a student just broke it about 20mins into the lesson. It was AWESOME.

      Combinatorics questions are great – I think that there could be a way into them as an application for indices – something to think about eh?

      Thanks for dropping by!

  2. Kev Lister says:

    Top notch as always Mr D… got to have a look at Des Man πŸ˜‰

  3. I can’t count the number of times I have told my students math is not a spectator sport. I thought I coined the phrase. πŸ˜‰ I couldn’t agree more.

    • nik_d_maths says:

      Thanks Sabrina! It’s a struggle sometimes to get the students to understand they have to DO Maths rather than it just happening in front of them. It’s a good battle though!


  4. Wendy Creek says:

    I saw that Des Man activity on the Desmos site-can’t wait to get into that. And thanks for the link to the “patio” task-that looks like one of those things that starts out simple but can go a whole lot of places.

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