Can differentiate with double digits (double digit by double digit multiplication or even fractions). This site has great math projects. This can be done with nails in a board and colored yarn. Makes a great pricture too.
DIY String Art Projects - Whale Tail String Art - Cool, Fun and Easy Letters, Patterns and Wall Art Tutorials for String Art - How to Make Names, Words, Hearts and State Art for Room Decor and DIY Gif (Diy Art For Teens)