jack

I didn't use either. But there's a limit to how much calculation in your head is virtuous; insane amounts of mental arithmetic is a valuble skill, but isn't really maths. Muppets use calculators to solve quadratics, but if a question is complex enough it's a valid mathematical technique to solve it numerically, possibly using this to inform later abstract work.

Remind me again what you do for five hours a day? :p :)