Math

Maybe this is because I'm a math genius, but it amazes and slightly annoys me when people cannot do simple estimations of math problems without a calculator. I'm not talking about getting an exact answer, but I don't understand why, for example, if you ask someone to divide 100 by 11, they can't come up with 9 as a rough estimate. This happens daily in my statistics class when I give close-to-exact answers to math problems and everyone else stares at me like I'm the one with the problem.