Another installment from my Fun With Folding series: paper pyramids!
First, start with a triangular cut-out. Construct this triangle’s medial triangle by connecting the midpoints of each side. If you don’t have a ruler handy, just fold corner to corner, and crease in the middle to find the midpoint of each side!
Now, fold up the sides and tape them together!
The best part about this activity is that it doesn’t always work! Finding out which triangles this will work for, and which it won’t, leads to lots of good mathematical questions to explore!