Trapezoid (half hexagon or 3 triangles) (Red) that can be matched with three of the green triangles

McFarland, Matt (9 December 2013). "The childhood toys that inspired female engineers and scientists". The Washington Post . Retrieved 10 December 2013. All the angles are multiples of 30° (1/12 of a circle): 30° (1×), 60° (2×), 90° (3×), 120° (4×), and 150° (5×). a b Walter, Marion (December 1996). "letter". Mathematics Teaching (157): 3 . Retrieved 3 May 2020.

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The EDC Teacher's Guide continues: "Many children start by making abstract designs — both symmetrical and asymmetrical. As play continues these designs may become more and more elegant and complex, or they become simple as the child refines his ideas."