What's Happening?

Shapes are added to other shapes. Can you see what is happening? What is the rule?

Problem

Image
A pentagon.

   

 

We started with this pentagon.

Added a triangle:

Image
The pentagon from the previous picture, with an equilateral triangle along the bottom right side.

Then another one:

Image
The previous image with an added triangle along the top side.

What would come next, and why?

 

Can you invent something like these for your friends to solve?



pdf is available here