Equilateral TrianglesTask 170 ... Years 2  8SummaryDesigned to invite younger students to think 'outside the square' this task hints at both algebraic pattern and the idea that three dimensional objects are made from flat surfaces which have familiar names. The doors it opens are extensive. The task is a partner to Six Square Puzzle which offers related challenges in the context of squares. 
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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 solutions to Questions 1 and 2 are: At this point the students might consider they have finished the task, but no. It is important with every task that students are encouraged to see that there can be more. For example, in this case we could suggest:
Questions 1 and 2 can also be extended with, in either case, questions like this: There are two triangles in this 'chain'. Extend the same chain so that it has 3 triangles, ... 4 triangles, ...10 triangles.
Number pattern work with triangles is extended further with Task 178, Match Triangles, and Task 179, Unseen Triangles. Challenge 2 suggests a number pattern too. It is a template for making a new equilateral triangle from 4 unit triangles. That means that four copies of the Challenge 2 result would make the next size equilateral triangle and it would include 16 unit triangles. But how many triangles altogether in this larger diagram? This mathematics is extended in Task 42, Triangles Around Triangles and leads to a different algebraic link in Task 186, Tetrahedron Triangles. In a different direction, Size 1 is the original unit triangle. Size 2 is the Challenge 2 result. Size 4 is this new triangle (why Size 4?).
In this interpretation of the Challenge 2 result, the equilateral triangle grows as the construction pattern repeats. This type of tile  one that selfreplicates  is called a Reptile. A 'sphinx', is another Reptile and Task 166, Sphinx, is explored in huge detail as a model for exploring the mathematics of Reptiles. Trisquares are Reptiles too and Tricubes carry the same mathematical questions into three dimensions. Lastly (or is it?) the Challenge 2 result opens the door to Value Relations questions such as:

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. 
Straws or popsticks or similar material and a little blutac per pair is all you need to turn this task into a whole class investigation that will allow you to take any of the directions above. The investigation could also be supported by writing Investigation Guides that provide a set of further questions to lead students into any of these directions. When you have created and trialed Guides for this activity we would be happy to share them through this cameo. At this stage, Equilateral Triangles does not have a matching lesson on Maths300, however Lesson 107, Newspaper Shapes, explores making 2D patterns and 3D objects with newspaper tubes and Lesson 164, Match Triangles, uses newspaper tubes and popsticks to explore more deeply the algebra opportunities which arise from the Question 2 solution above. 
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. 
Equilateral Triangles is not in any MWA kit. However it can be used to enrich the Space & Logic kit at Years 3/4 and the Pattern & Algebra kit at 7/8. This task is included in the Task Centre Kit for Aboriginal Students with the title Triangles Galore. 