Mathematics isn't always funny by itself, but that's no reason to study it without laughter.

One day, the teacher gave us what looked like a very simple problem. Maggie and I each have ten pence. I give Maggie five pence. How much more money does Maggie have than I do now? I smiled. That's easy, I thought. I put my hand up before anyone else. "Five pence," I answered confidently. The teacher smiled. "Think again." I looked at the numbers once more, but I still couldn't see what was wrong. Answer: "When you gave Maggie five pence," I began, "you had five pence less than before, when you and Maggie had the same amount of money." "But Maggie had five pence more than that original equal amount." "Exactly. So the difference between your amounts didn't increase by just five pence. Maggie's amount went up by five pence, and yours went down by five pence." "That means the gap between you became ten pence."