Math Skillz

A couple weeks ago at a garage sale I was negotiating for records and a mirror. The offer on the table:

Beethoven's Symphonies for $5 and a long mirror for $5.

I told the guy, "Look, I'll give you $4 each for the Beethoven and the mirror."

"No, no, no," he said, "I already came down on the Beethoven. That costs $5. But I'll tell you what - I'll give you the mirror for $3. How about that?"

"Okay." I said.