Math Snake 9 blocks

I love math puzzles, and with the help of Ken Irvine of NJ, we came up with the Math Snake idea. The idea is to rotate them until there is a correct equation on all 4 sides of the blocks. The equation is read from left to right, regardless of operation priority. There is a 9 block model (here) and also a less difficult 7 block model offered on a different listing. They are high quality all wood construction with deeply burned laser engraved numbers from our shop in Spring Hill, FL. The blocks stay as a string but will rotate individually. The 9 block model is very difficult with 16.384 possible permutations of the blocks but only 1 correct solution. The 7 block model is a easier (but not easy) with 1024 possible permutations. Ken Irvine wrote the program to develop the math layout on the blocks. As it turns out there are a number of possible ways to burn the numbers on the blocks and still have a unique solution. So there are 20+ different models we can offer on each of the 7 block or