If you ask me, this sort of testing is essential. It amazes me nowadays, the standards of mental arithmetic. As I'm only in my mid 20's I come from the generation whom carry a 'plastic brain' i.e., one made by Casio. Having said that, from an early age my dad has peppered me with mental arithmetic, so I feel quite comfortable with mental calculations.
But the amount of people I've trained with, and flown with - whose mental arithmetic is sub-standard is astonishing.
Flying a jet is a numbers game - just as Pilot Pete stated. I'm nearly always calculating something in my head; rate of descent, Top of descent point, fuel burn etc. There’s nothing worse than when you’re pilot flying in the sim with someone with below par mental arithmetic – just adds to work load.
I feel that there are a few in this industry who 'slip through net'. They are in the minority, but still present nevertheless.
That's why I believe aptitude testing including maths in essential. The inability to work out fractions is a little disconcerting for such technically minded people.
Anyway, apologies for dragging this post further off topic. Back to it....