My ex-wife was.....wellllll...let's just say "not the sharpest knife in the drawer." Actually, she was about as sharp as a marble.
Once we were talking to a salesman about buying some new furniture. He checked his calculator, then told us, "Well, folks, you pay $50 down, and then you don't pay anything else for three months." She gave him an incredulous look, and said, "How the hell did you find that out?" 8-)
She also had a problem with getting her quotes just right, too. She told me once, "OK. You've made your bed. Now lie about it."