The strange thing is, it's not always apparent whether someone is functionally illiterate or innumerate. It's disturbingly routine, in the US at least, to have

The strange thing is, it's not always apparent whether someone is functionally illiterate or innumerate. It's disturbingly routine, in the US at least, to have a degree with barely even a grade school understanding of math. And although total illiteracy is uncommon among high-school and college-educated people, you would be surprised how many can't write a normal paragraph or follow a written argument. You can't necessarily see this with normal public or workplace interactions, but it is real.