Donuts are generally round with a hole in the middle unless they’re filled, but have you ever stopped to consider whether or not the hole is optimally sized? Mathematician Dr. Eugenia Cheng did, so she used calculus to figure out the right size for the hole. She first determined that a bigger hole increases the surface area creating a crisper donut.
She then went on to measure the “squidginess” and “crispiness” ratios of the donut to determine that a ratio of 3.5:1 which comes along with an 11 mm hole makes for perfection. Of course, your tastes may vary but I’ll buy into any science that uses a term like “squidginess” to prove its point.