Mar 312016

Montessori Lesson


4 to 4.5 years approx.


Box 1 is a triangular box  which contains the following 10 triangles:
4 red equilateral triangles with a black line on one of the 3 sides while the 4th triangle has black lines on all 3 sides.
3 yellow obtuse angle isosceles triangles with a black line on both sides of the obtuse triangles.
2 green right angle scalene triangles with black lines on the longer side of the right angle.
1 large grey equilateral triangles with no black lines.


To give the child the opportunity to experiment with various geometric shapes.


To discover, at a sensorial level, the various ways these shapes can be divided and combined to form other shapes.
For later work in Maths and Geometry.


Individual exercise done at a table or on a floor mat.

  1. Remove the triangles from the box, one at a time. Bring the 2 green triangles closer together and feel along each of the triangle’s black lines with the middle and index fingers. Fit the two triangles together by sliding them together on the mat so that their black lines match together.
  2. Continue in this way with the yellow, then the red triangles.
  3. Check that the triangles are correct by placing the grey triangle on top of each new triangle and verifying the match.
  4. Show the child how to return the triangles back in the box in order: red, yellow, green, and grey.

  6. Give a three period lesson on the apex, base, bisector, median, align


The black line and the large grey triangle.

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