Actually, the dumbest people I've ever worked with have been quite good at doing math.
I picked cases in a freezer warehouse where each picking team got paid 8.25 cents for every case they picked. These guys could look at a truckload's pick stickers, read the number of cases in the load, estimate (based on how large the printed stack was) how long it would take their team to pick it and then estimate to within $0.25 how many dollars an hour they would make on that shift- and then how it would affect their 8 week average of pay. They could effortlessly calculate how quality audit results would affect their pay and know exactly how to bring their audit results into the needed range.
They could also look at the shift's work and know immediately if splitting an 8 ball would pay for itself in increased productivity. I did my own math (rather, I applied it outside the confines of the immediate shift) and was one of the few who didn't consider coke a PED.
Totally unrelated to that, I was one of the very few on night shift who hadn't lost his license to a DUI- which oddly enough raised my pay by getting me into gigs that involved driving to other warehouses. I didn't have the seniority to snag those assignments, but I was legal to drive.
So simply saying "they can't do math" ignores the problem. They can do math, they just can't think things through. Jamie Lee Curtis put it very well:
