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The bisected equilateral triangle ($30-60-90$) is an important shape for students to become familiar with. Each of the $4$ rectangles is made from $2$ equilateral triangles and $2$ isosceles triangles. Together one of each of those two, makes the $30-60$ right-angled triangle.
This problem forces consideration of the side lengths in surd form, and provides an opportunity to become familiar with manipulating surd forms.The switch from one quantity as the given unit to another, emphasises that the choice of unit is a choice for the problem solver and can be considered so as to make the relationships within a problem as clear as possible.
Preceding these questions with 'playtime' using cut out triangles to form patterns may be a very useful preliminary for many students.
Include shapes that have holes, and suggest/invite challenges with respect to that 'hole'.
And maybe include the challenge to lose the 'hole' but keep the square.
What is the area of the yellow equilateral triangle in terms of its side length ?
There are a number of activities which can provide valuable auxiliary experiences for students working on this problem :