Well, this is a configuration I came up with for the 3x3x3 cube. I am not sure if anyone has done this before, but if not, let's call this the "calcube I
The background color should be white, the reason I placed the colors was to show that the six sides are divided into three pairs. Each pair consists of three simple math operations.
The maths operations may be simple, but figuring them out (while solving the cube) is definitely not easy...!
(I tried it on an experimental cube of mine)
For consisteny (regarding the number frequency), I have placed the numbers 1,2,3,4,5,8 four times, the numbers 0,6,7,9 three times, while there are five addition symbols and four multiplication symbols.
(Moreover, there are three centre pieces with a zero, and the other three have the multiplication symbol)
I hope you like it!