Montessori Constructive Triangles + DIY Printable

What are the Montessori Constructive Triangles?

The Constructive Triangles offer children hands-on exposure to concepts in plane geometry. The materials include two rectangular boxes, a triangular box, a small hexagonal box, and a large hexagonal box, each housing triangles of varying sizes, forms, and colors.

Through the use of Constructive Triangles, children learn the relationships between triangles and how they make-up other two-dimensional shapes.


  • Watch the following videos (click the hyperlinked texts) to learn how to present the lessons:
    • Rectangular box A
      • Work with 2 yellow equilaterals, 2 gray right-angled scalenes, and 2 green right-angled isosceles (match, superimpose, and align black lines to make a shape)
      • Work with 2 yellow right-angled isosceles, 2 yellow right-angled scalenes, and 2 green right angled scalene triangles (do the same as i)
      • Work with the remaining red triangles and form a shape.
    • Triangular box
      • Work with green triangles (superimpose and put the black lines together)
      • Repeat with yellow triangles, then with the red triangles.
      • Do the same with the gray triangles.
      • Language lesson: Base, vertex, altitude/height (with the gray triangles), center of the triangle (with the yellow triangle), midpoint of the triangle (with the red and gray triangles)
    • Large hexagonal box
      • Form a rhombus with the red triangles; then form a parallelogram with the gray triangles
      • Form a hexagon with yellow triangles with one line each and the large triangle
      • Form a triangle with the yellow triangles with two lines each
      • Superimpose the triangle on the inner triangle of the hexagon, then show the child each rhombus formed by sliding them away, forming 4 rhombuses
    • Small hexagonal box
      • Form a rhombus with the red triangles, then form a trapezoid with the green triangles, then form a hexagon with the gray triangles.
      • Show the child that the gray hexagon can be split into three rhombuses and superimposes the red rhombus.
      • Ask the child to reform the hexagon then show that it can be split into two trapezoids and superimposes on the green trapezoid.

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