How do you explain...?

[Nystul]

May not have anything at all to do with intelligence. It could be something like dyscalcula, too much stereotype threat during her education or even just a terrible education.

It's not a fair shake anyway. It is a unit conversion issue, like the attacks per second. We spent the entire 9th grade science class working on problem solving by unit conversion, which suggests that it is anything but common sense for a lot of people. 80 x 1 is absurdly easy. Failing to recognize the problem that needs solving is a common trap. People make stupid mistakes all of the time but in the old days there were only a few witnesses. Now the whole world gets to see how dumb everyone is on twitter, youtube, etc.