A Mathematician Writes

One of the first things that children learn in maths is to do a quick check of their answers. Not quite sure if your calculation of 6.9574635 times 4.085647 is correct? Well, 7 times 4 is 28, so your answer really ought to be pretty close to that.

Common sense, right?

Wrong: Amazon says it's a brilliantly-novel idea that no one has ever had before in the history of the universe - and they have a patent to prove it. Words - and numbers - fail me. (Via Techdirt.)