I made these self correction addition pie for the preschool age. One side has the addition problems and you clip on the clothes pin with the answer. When you turn the pie over, if your answer is correct the color should match. It’s also good to just match the colors if the child is not quite ready for the math.
I have included a copy of the addition pie to this post. I used paint chip samples to add the colors. You can find cheap clothes pins at the dollar store and just glue the rods in place (they come apart easy) I printed these two to a page on cardstock.