Yesterday in class my class was identifying triangles. They picked it up pretty simple since we have been working with angles for the past week.
I pulled out the construction paper for a little math art project to show their comprehension. Students took a rectangular green piece of paper and glued it onto the paper as a stem. They then took a piece of pink construction paper and cut out 7 triangles of different sizes. They had to label the triangles as acute, obtuse, or right, and then glued them onto the top of the stem as the flower portion.
It was easy, fun, and I was able to see exactly who still needs a little work with the concept. I made up this freebie version in case you don't have access to construction paper, or want a cute border when you have the kids add their construction paper. I hope it helps you!