Paddy decided to decorate his bedroom. He wasn't sure how many rolls of wallpaper he would need but he knew that Murphy who lived next door had recently done the same job and the two rooms were identical in size.
"Murphy," Paddy asked, "How many rolls of wallpaper did you buy for your bedroom?"
"Ten" said Murphy.
So the fellow bought the ten rolls of paper and did the job. It looked wonderful, but he had 2 rolls of wallpaper left over.
"Murphy," he said. "I bought ten rolls of wallpaper for the bedroom, but I've got 2 left over!"
"That's funny," said Murphy. "So did I."