What's important isn't being able to do it right quickly the first time. It's having a strong habit of checking your work as you go, both at a low level and a high level. (Kinda like unit testing and integration testing...)
Fast arithmetic and algebra are fairly particular skills. As one progresses into new world of math, the calculations and operations may be completely different from what's been practiced, making the fast math less useful. But a good habit for careful progress is completely general!
Fast arithmetic and algebra are fairly particular skills. As one progresses into new world of math, the calculations and operations may be completely different from what's been practiced, making the fast math less useful. But a good habit for careful progress is completely general!