I learned about these on a video on Numberphile. . In the video they said the magic words “no longer available” and that was it, we had to make our own. Josephine Sheng designed these way back in 2017 I think, and we just never posted. We don’t like “tricking” people, but if you have a good half hour you can explain how these work and even make your own from popsicle sticks. We did that with 4th graders at Cedar Creek Elementary this spring.
Check out the 1st, 2nd and 4th numbers in the columns. they all add up to 18 always. So with the sticks set up adjacent to eachother they look like 4 4 digit numbers. What do they add to? Look at the 3rd row and put a 2 out in front, and take away 2 from the ones column. That’s the total.
Our files are here: