Land of ETTask 145 ... Years 4  10SummaryAn imaginative story shell drives this task, but far from being trivial, it leads to the very core of the number system. In fact, beyond that to structures that link apparently different parts of mathematics. And yet, because of the colour, visual, concrete aspect of the presentation it can be tackled successfully from middle primary. The idea is simple  if a little unreal. A kingdom which has an alphabet of only two letters. That makes from some very long words. The king and queen are finding this all a bit tough, so they introduce rules to shorten words. Perhaps by accident, perhaps through regal wisdom, there rules result in surprisingly few words. 
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IcebergA task is the tip of a learning iceberg. There is always more to a task than is recorded on the card. 
The first question on the card is about encouraging exploration of these new language rules. The simplifications are:
Students are then encouraged to explore words of their own and finally challenged to find out just how many unique words remain the language. Most will begin randomly making strings of letters and trying to shorten them. Perhaps they will have to be encouraged to reread the rules that say 'removed (or included)'. There are some words that can only be simplified if by using inclusion at some point. For example:
ExtensionsWhat happens if we add two of the six words together?What are the possibilities?
Wow, another surprise! The answer is always one of the six words. Well perhaps not such a surprise since we were pretty sure they were the only words in the language. Are there any patterns in the table?
The structure of the ET language has now become closed. That's different from our number system which is infinite.
With the imagined clock timer, if it is already at 5 and you add one more section you get to 0. And then one day the mathematician might be playing around with an equilateral triangle and realise that no matter how it is:
Hey, that's a closed system too. I wonder how many different transformations there are in this system? ... and what happens when they are combined? 
Whole Class InvestigationTasks are an invitation for two students to work like a mathematician. Tasks can also be modified to become whole class investigations which model how a mathematician works. 
To turn this into a whole class lesson, the objects you use need to be yellow and blue. Not many schools will have sufficient counters or cubes, or tiles of these two colours, however schools with Poly Plug have just the right resource. One yellow/blue board between two will do the job. Use the lesson to highlight that mathematicians love to find structures underlying mathematics and to highlight similarities and differences between the ET system and our number system. For more ideas and discussion about this investigation, open a new browser tab (or page) and visit Maths300 Lesson 65, Land of ET, which also includes an investigation guide for the transformations of the equilateral triangle. Visit Land of ET on Poly Plug & Tasks. 
Is it in Maths With Attitude?Maths With Attitude is a set of handson learning kits available from Years 310 which structure the use of tasks and whole class investigations into a week by week planner. 
The Land of ET task is an integral part of:
