It's not saying that it doesn't know how, it's saying that the division is undefined. Probably that means you tried to do a 0/0.
By the way this is running fine for me so far, though it hasn't made any trades yet.
I was able to check this. I forced it to zero and tried and it threw a divide by zero exception.
I think the problem is actually a non-terminating decimal expansion.
I'm looking into how to guard against that. Probably with rounding since there is only a certain amount of precision we really need to worry about.