Okay, here's one that kept me up all night.

I know that some types of potatoes are good for baking, and some types of potatoes are good for boiling, and some are good for frying. Others are "all-purpose" potatoes, presumably good (or bad) at everything.

But... how do you know which is which? I mean, if I handed you a random potato, and you didn't know what variety it was, and maybe you'd just found out that there are more than three types of potatoes in this world... how would you know what to do with it without asking?