I really have to sit with him and explain stuff as we go. I had ordered it thinking I would show it to him in a year or two but he didn't want to wait
We reason out how to solve the problem and then look up the formulas in the secret notebook. The game also allows you to "buy hints." DS can't do all the calculations yet but I let him do the ones he can do. Sometimes he comes up with his own methods (like drawing a diagram and estimating or something.) If he wants to use my calculator to figure it out I let him do that too.
You can see a demo on the CTY website.
Oh, that reminds me, another fun math thing is calculation tools like abacuses, slide rules, calculators or finger calculation tricks.
