Only a quarter stupid!

We went to visit my girlfriend at work. She's a bartender and it was Mother's Day so the place was pretty dead. But we were drinking beer and having a wonderful time. Derek goes to the jukebox to play some music. After about 15 minutes I turn to him and tell him that he has great taste in music and that I must have taught him well. He replies "I'm not completely stupid as you seem to think I am!" To which I reply "I don't think your completely stupid; only a quarter stupid!"