Students will learn how to identify symmetric figures and count lines of symmetry and rotational symmetries. Conclude by giving this challenge to your students. My solution is based upon *Solution 1.* Denote corner as C and side as S. I started by thinking about all the ways I could place the 3 blues. There is 1 way for CCC, 2 for CCS, 2 for CSS, and 1 for SSS. Here's how I drew the 1 CCC and 2 CCS:

X X X
O O X O O X
X O X X O O X O O ...

If you're very careful, you can also solve this problem by placing the 1 green first, as seen here. My way is a bit nicer, because after placing the blues you can figure out all possible positions for the green in your head. That is, you will end up drawing the 6 arrangements for the blues instead of all 12 arrangements for the blues and greens.

Concude by giving your students this challenge:

How Many Triangles Do You See? Challenging Puzzle by MindYourDecisions: When providing the solution, give both the solution found in the video, and my more elegant solution, which is as follows: Draw the lines of symmetry, a horizontal line and a vertical line. Consider one quadrant, whichever one you like. There are 4 triangles that occur entirely in that quadrant. These 4 triangles will occur 4 times, because there are 4 quadrants. There are 2 triangles which are cut by the vertical line of symmetry, but not the horizontal. These 2 triangles will occur 2 times, because there are 2 halves. There are 6 triangles that are cut by both lines of symmetry, and thus occur only once. Hence, the total number of triangles is

$$4 \cdot 4 + 2 \cdot 2 + 6 = 26$$