What's the most useless thing you've learned in school that actually came in handy one day?

Didn't come in handy, but more of an epiphany. So back in high school, I learned that the majority of Southeast Asians are lactose intolerant. Honestly it was one of the most boring topics I've had to sit through.

Later in college, a couple of my Southeast Asian friends invited me to a culture night at the last minute. I decided to bring brownies. Who doesn't like brownies? Then I noticed at the event only like two people took a piece, while everyone else tried other foods. That is when my third eye opened and I realized why they're not eating the brownies.

I started inquiring of the other more popular dishes and sure enough it was dairy free.

/r/AskReddit Thread