That shape is known as a tetrahedron
Thanks. I have included "tetrahedron" in the answer.
My answer would have been to use 3 matchsticks to divide the single triangle into 4 smaller triangles. This keeps it a 2D puzzle,
Thanks, Dawie! Your website really helped with my homework!It's really useful and I hope more people can find it. :)
You are welcome Lily.