I am no student of math; but nevertheless, one wonders where reality begins and ends with this problem. Is the difference between .9r and 1 real, or is it just a side effect of symbolic manipulation? The 1/3 + 1/3 + 1/3 = 1 yet arguing .3r + .3r +.3r != 1 would seem to speak to a quirk of manipulation, not reality. And justify how you can get from .3r to 1/3? I'll answer that: by stating that 1/3 is the
that will result in .3r when using the decimal representation system.
After all, in a computer decimal arithmetic is not really calculation, it's symbol manipulation. The only "calculation" occurs later in analysis of error.
Pi has no finite writing in any symbolic system save the Greek letters, yet it is nevertheless real ... but it can be better represented by the algorithm that "determines" or "computes" it. We are forced to employ this algorithm to transform pi into something suitable for calculation with other "numbers". So is pi a number or a process?
Good questions. Here's how I see it.
For most things, if it's close enough, that's fine. Horseshoes and handgrenades are like this

Yes, 1/3 and pi represent processes as well as .3r etc.
These are finite representations of infinite processes. They exist as finite values only symbolically and not when they're expanded into an infinite form.
The number 1 doesn't represent a process though because it's a fundamental unit from which the others are built. We have to select something to remain absolute so we can build relationships upon it and 1 is the symbol for unity in multiplication versus the 0 for unity in addition. Division and subtraction are the inverses of these and only apply when such inverses are finitely computable (for example, you can't divide by 0, simply by definition, though some could estimate what a value divided by 0 would be, for example x/x=1, except when x=0, in which case you can generally still assume the answer is 0, but not always)
For example, we might say that 1/0=infinity, but think about this for a second ... is that actually true - even if we had someone subtracting 0 from 1 forever, would they ever be able to reduce 1 at all? Realistically, no, unless that was the amount of time it took that person to think of a better way to represent the ratio 1/0. So we can't really know if the vague notion of "infinity" is even correct in this case.
You can't redefine 0 or 1 as processes. They can only be inputs and outputs and not functions.
For example, y=x/3 is a function. 3/3 is 1 and an exact result that can be computed by definite in finite time, but 2/3 is an intermediate value that represents an irreducible computation. It's a symbolic representation of an infinite computation.
Once again, you could subtract 2 from 3, get 1, then rescale things so you have 10, then subtract 9 and get 1 again and then rescale by 10 etc. etc. etc. and there would always be an error in the answer, not much different than trying to subtract 0 from 1 forever, except in this case the relative weightings of the digits decreases,
so it does approach a fixed value but that fixed value still has an infinite representation and can't be symbolically manipulated directly in that infinite format, because any finite quantization of it leads to errors and approximations. So you can write 2/3 and be precise and not find errors, but you can't try to treat it the same as .666666..... without introducing errors (notice everytime people write it, they always ignore the last digits and you can see when they manipulate this value they either have to show a limited example where the importance of the least significant digits becomes undeniably trivial or they mask the importance of them by no recognizing every time they shift the value left the errors grow in significance).
For example, 10*.9r is not the same as 9+.9r, because any errors in the 10*.9r are now 10 times as significant as the errors in .9r so the error terms no longer match. Now if we just say the errors are 0 so that 10*0=0 then the problem is simply ignored.
To work with this correctly an error term should be used and the boundary for the error analyzed as the expansion continues so that you can be certain the error does not grow to be more than infinitesimal, but this requires that you specify how digits the expansion occurs to and then the manner in which one expansion occurs versus a different one can result in the error never approaching zero.
As long as some deterministic process can be specified that reduces their evaluation algorithmically (which by definition cannot take an infinite number of steps) to another finite representation, then we can bypass the need for any infinities to exist and everything remained a deterministic value.
But infinity is inherently nebulous and ill posed to work with in many processes.
For example, is infinity+1> infinity or does infinity/infinity=1 or what about infinity+1/infinity=1 or does 1/0=infinity, how about 0/0=+/- infinity or maybe 1 etc.
The way to avoid these is to avoid using infinite representations. As long as you can remain within computable values, then mathematics works great, otherwise you have to create rules that can be arbitrary and unprovable simply because the assumptions could easily change from one calculation to the next and introduce unresolvabled paradoxes.
As long as the errors remain infinitesimally small, you can generally toss them away, as is often done in calculus but calculus acknowledges the problem as well and places restrictions on when the result is valid.
So yes, as long as you're able to keep the values distinctly seperated and round out the errors in the end, then it works fine but if the result is sensitive to infinitesimal differences then you have to maintain a way, during the calculations, to untangle them in the end or you're left with indeterminant results.
For example, if we take the arcsin of
exactly 1, the result must be
exactly pi/2. The 1 in this case cannot be anything over 1 or a result is impossible to calculate. On the other hand, the function is extremely sensitive to small changes below and, for example, the slope of the output between 1 and .99999 is 1000*2^0.5 or ~1,400. In cases with functions this sensitive, you can't leave unresolved error terms in place or they explode into things like trying to divide 1/0 etc.
So you have to keep track of which terms become most significant in the limits and track them as they approach to see which terms dominate. This isn't provided by the identity .9r=1 and so it can only be treated as an unprovable and questionably valid equation for limited uses only (to make it more explicit you could write .9r~=1) once you've thrown away the details of the process that generated the infinite sequence, you can no longer determine the relative signifance of the error term associated with it and I hope some of my previous posts demonstrated this.
Also, it may not actually be a quirk in the mathematics of infinity but represent a deeper understanding of mathematics that goes generally overlooked. Not all infinities (or infinitesimals) are created equal and transitions between them and finite values have many interesting properties.