Models for triangular numbers {1, 3, 6, 10, 15, ..., n(n+1)/2}. They can also be used to model tetrahedral numbers {1, 4, 10, 20, 35, 56, ..., n (n+1)(n+2)/6}. The spheres are intentionally welded with each other for easy use with students. The activities can be used at many K-12 levels, depending on the instructional goals. The formulas can be established using mathematical induction; they are as interesting as the visual structures. To print, please use raft for better adhesion to the bed.
| T1.stl | 1.1MB | |
| T2.stl | 2.0MB | |
| T3.stl | 2.8MB | |
| T4.stl | 3.5MB | |
| T5.stl | 4.3MB | |
| T6.stl | 5.1MB |
