To begin this project, I gave each child two triangles. I then challenged them to figure out how to use these two triangles to make a square. Most of my students figured this out quickly. After that, I gave each child four triangles and asked them to figure out how to use all four to make a bigger square. It was fun watching them slide the triangles around until they figured it out. Once they had this figured out, I had them start building their castle out of triangles.
It's funny because this project seemed extremely simple to me, but my first graders absolutely LOVED every minute. They were extremely proud of their castle creations. Some of my students even drug their parents in after school to show off their artwork.