Even if LLMs get better at arithmetic, they don't seem like the right tool for the job.

LLMs might never be able to crunch numbers reliably, however I expect they should be very good at identifying the right formula and the inputs for a problem ("i need the answer to x*y, where x=12938762.3 and y=902832.2332"). Then they can call a math engine (calculator or wolfram alpha or whatever) to do the actual computation. That's what humans do anyway!