[cross post with OpenEdToolbox.com]

I always try and include some extra fun lessons in the last week of term that revise a range of topics students are familiar with. In addition, it is always extra special to be able to introduce some new concepts at the same time. I got the idea for this lesson from the Black Douglas Mathematics Centre, an incredibly rich resource closely linked to Maths 300, but it is free! If you haven’t had the opportunity to look at these resources as a school, please take the time to do so. They are just packed with open-ended, purposefully engaging lessons with a focus on problem solving throughout.

I taught this lesson in the last week of Term 3, and found myself wishing we had the time to investigate more!


Smarties! Introducing Negative Numbers

Focus on problem solving throughout


  • 600g pick n’ mix smarties (or M&M’s)
  • paper bags with random selection of approx. 30 smarties per pair of students
  • 10x10mm grid paper (enlarged to A3)
  • calculators

Lesson content:

Our Learning Intention was based on using our number skills to experiment with negative numbers (which my students weren’t familiar with previously), but the learning experience included so much more, including: data-collection, chance, graphing, number patterns  and calculator use. Our Success Criteria was to effectively show addition and subtraction using negative numbers on a number line.

I went to my local supermarket and bought 600g of pick n’ mix Smarties, which was enough for around 30 Smarties per pair in a class of 24 students. I also gave each pair a 10x10mm sheet of grid paper, enlarged to A3, to assist them with the graphing of their random selection of smarties.

The rules of the game were as follows:

  1. Each pair was to count their smarties and each player record this number in their own scrapbooks as their starting score.
  2. All of the smarties are placed back into the paper bag.
  3. Students take smarties out one by one, each student guessing which colour will come out next.
  4. A correct guess scores +2 points
  5. Incorrect guess scores -2 points

The students kept a record of the addition and subtraction in their scrapbooks:

Keeping a record of the addition and subtraction

Prior to this, I encouraged each group to build a simple column graph to refer to during the game – I had little input, simply observing and taking some anecdotal notes about graphing skills, axis labelling etc. Some of the graphing was interesting!

Number patterns Graphing

The students amazed me with their creativity when they began playing the game. Nobody ate any, they were far too valuable! Instead, they rebuilt their graph to assist them with correct guessing.

Data collection Calculator skills

We had a great discussion about which strategy/strategies we were using from our Mathematicians’ Toolbox (an invaluable tool from edgalaxy.com, which can be found and printed here)

As students waded into unfamiliar negative number territory, some were able to successfully apply prior knowledge. I stopped other students and encouraged them to use a calculator and a number line to support their calculations.

The discussion at the completion of the lesson was based on meeting our Success Criteria, but also somewhat disturbed by the munching of half-melted smarties (‘no thank-you, I don’t want one’). As I said, I wish we could have used this as a springboard for a follow-up lesson, but it was a great one to explore in the last week of term nonetheless.


I’d love to hear your comments, suggestions and reflections below. What resources do you use to enhance your math lessons? Have you found any other open-ended resource banks like Maths300? What else do you use to brighten math lessons?


Feature image courtesy of Flickr, gadl.

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