This is a material that I do not yet own, but felt it was necessary to cover, especially with having discussed the Binomial Cube yesterday.
The Trinomial Cube should be delayed until Upper Primary, when the child has a firm understanding of all preceding Sensorial materials, including the Binomial Cube. While the Binomial Cube has eight parts (cubes and prisms), the Trinomial Cube contains twenty-seven — so the delay between the Binomial presentation and Trinomial presentation can be longer than a year based on the child’s development.
The methods of demonstrating and teaching with the Trinomial Cube are exactly the same as for the Binomial Cube — the only differences being that we now have three (unknown) factors, rather than two, and twenty-seven pieces to fit together rather than eight.
While there are better “quality” videos out there, I love this one as it shows a child teaching another child, which is a unique feature in Montessori education. I think this must have been taken during a parent night, because the background noise is definitely not appropriate for a learning environment.
While it is possible to DIY this material, it can be purchased inexpensively and it can be used from the age 4 through high school, which makes it a worthy investment for me. The cheapest that I’ve seen it is $31 to $37.