What lack of basic knowledge in college students surprises you the most?

I'm talking about those moments that make you think "where did you go to high school?" or "how did you get into this university?" I'll start:

Not knowing how to do metric conversions. I'm not talking about imperial to metric and vice versa, but metric to metric, such as converting from milliliters to liters.

Not knowing how to use percentages.
"What is 30% of 40? No, it's not 1200."
"Let's try this again, can you convert 30% to a decimal? Okay, multiply that by 40. Wait, how did you get .12??"