Just like humans. Try to get regular people do e.g. add 15-16 digit numbers (where is typically where I'd see GPT4 start to get "sloppy" unless you prompt it the way you would a child who's learning and is still prone to get annoyed and wonder why the hell you make them to it manually), and see how many start making mistakes.

I find it really comical that this is what people complain about GPT over - there's zero benefit to get LLMs to get good at this over other tasks. To the extent we get it "for free" as a benefit of other learning, sure, but when we make kids practice this over and over again to drill doing it without getting sloppy, it has traditionally been out of some belief that it's important, but a computer will always have a "calculator" that is far more efficient than the LLM at its disposal and it's idiocy to care about whether it does that part well the tedious and hard way or knows how to describe the problem to a more efficient tool

I also find it comical that people use tasks where LLMs behaviour is if anything mot human-like, in its tendency to lose focus and start taking shortcuts (before GPT4 started writing Python instead, it'd for a while try really hard to not give you a step by step breakdown and instead clearly take shortcuts even you prompted it heavily to reason through it step by step), when presented with stupidly repetitive tasks as examples of how they're not good enough.