Material name: Constructive Triangles: 12 Identical Blue Triangles
Area: Sensorial & Geometry
Purpose & developmental benefits:
The set of 12 Identical Blue Triangles allows children to explore plane geometry through hands-on construction, rotation, and reconfiguration of identical triangles. Children discover that many different shapes can be formed from the same basic shape, leading to a deeper understanding of structure, area, form, and geometric relationships. This material provides important preparation for abstract geometry and later algebraic thinking.
Skills supported:
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Combines two or more triangles to form quadrilaterals and polygons
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Recognizes equivalence, equality, and similarity among constructed shapes
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Observes and compares edges and angles to achieve precise fitting
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Develops spatial reasoning and geometric thinking
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Refines fine motor skills, hand–eye coordination, and perseverance through trial and error
Recommended age:
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4–6 years (late Casa cycle)
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Used more extensively at 6–12 years for work with equivalence and area, once children are confident with basic constructive triangle activities
Material & design:
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Consists of 12 identical scalene right triangles, blue in color
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Made from Duron or birch plywood, painted on both sides for clarity
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Stored in a rectangular beechwood box with a lid
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Smooth wooden finish with rounded edges for safety
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Standard Montessori blue, with clearly defined edges for accurate construction
Use in the classroom / at home:
Children spread the triangles on a work mat and begin by combining two triangles to form new shapes, then gradually extend to three to six triangles or more. Teachers may initially suggest a few sample constructions and then invite children to explore independently.
Activities can be enriched by naming the shapes formed and linking the work to the Geometry Cabinet or geometry cards.
At home, it is best to offer short, focused sessions, ensuring the triangles lie flat and there is sufficient space for construction.
Typical extensions include:
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Creating larger shapes (hexagons, rhombi, parallelograms, etc.)
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Comparing shapes made from the same number of triangles
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Individual or small-group work in the geometry area
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Progressing to advanced Constructive Triangles and geometric drawing
