[blueblimp]

It's believable to me that a smart+motivated person whose reason for not knowing much math is lack of formal education could catch up a lot faster than you might expect. Educational pacing is generally designed for people who aren't smart and aren't motivated, so if you're both, you can go much faster.

Additionally, she was doing this at around 22 years old, which is in the age range that your brain reaches its optimum performance at learning new things.

She also wasn't starting from sixth grade math knowledge, more like spotty knowledge: she says she had learned some logic, algebra, and set theory.

It's annoying that she characterizes herself as a person who isn't smart/mathy/etc., when her story implies she has plenty of talent for it and just lacked the formal education. The vast majority of people do get a public school education or equivalent, and if they consider themselves bad at math, it's because they were having trouble learning it. If anything the story just demonstrates the dominance of talent+motivation over amount of educational background.

Edit: To elaborate, she says she expected math to be difficult because "I had heard throughout my life that math and physics were really difficult", not because she wasn't able to do well in her math classes. She says "I had the most difficult time possible taking intro physics and the beginning calculus courses", and yeah it's going to be challenging and a lot of work, but she doesn't say her grades came out bad in the end. The takeaway _should_ be that you need to be careful with second-hand opinions about what's difficult, because people vary so much in their aptitudes and interests.