A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

A large difference
A man went to the doctor's. The doctor came in and said,"Well, I've got some good news and some bad news. The bad news is that you have an inoperable brain tumor. The good news is our hospital has just been certified to do brain transplants and there has been an accident right out front and a young couple was killed and you can have whichever brain you'd like. The man's brain costs $100,000.00 and the woman's brain costs "$30,000.00." The patient could not help but ask, "Why such a large difference between the male and the female brain?" The doctor replied, "The female brain is used."