Consumers are no good at maths

In The 11 Ways That Consumers Are Hopeless at Math Derek Thompson looks at how consumers are easily fooled when it comes to determining a bargain or a fair price.

There are two broad reasons why these kind of tricks work. First: Consumers don't know what the heck anything should cost, so we rely on parts of our brains that aren't strictly quantitative. Second: Although humans spend in numbered dollars, we make decisions based on clues and half-thinking that amount to innumeracy.