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Sunday, October 18, 2009

The Fibonacci... WHAT?!?

So last week Lizzy and I were going on a walk around the neighborhood when she started noticing the house numbers.

"Look, Dad," she said, pointing to a house numbered 132. "If you just change the order, it's 1-2-3!"

A minute later, Lizzy noticed another interesting house number: 112. "Hey," she called out, "it's the first three Fibonacci numbers!"

Excuse me?

I froze in my tracks and looked, rather stunned, at this little 8-year-old blonde girl happily walking down the sidewalk. It was somewhat otherworldly. Ignoring the words that had just come out of her mouth, this seemed like a very normal afternoon walk. Happy, carefree, bubbly child. Nice weather. Concrete sidewalk. All very normal. But Fibonacci?!?

"Where did you learn about the Fibonacci sequence?" I asked.

"Oh, in some books," said my little bookworm.

But more than knowing the name of this mathematical phenomenon, she knew how it works. "You know, 1 plus 1 is 2; 1 plus 2 is 3; 2 plus 3 is 5..."

Where did this child come from? I hadn't even heard of the Fibonacci sequence until I read the Da Vinci Code when I was probably 35. And even then, I didn't retain in memory how it worked. To me it was some obscure spy code thing that math whizzes knew. But not normal people. So I ignored it. Then last year it came up at work and I later learned it wasn't so complicated after all. Just start with 1 (or zero, according to some people) and add the first two numbers to get a sum. Then add the sum and the previous number. Soon you have a sequence that goes like this: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, and so on. Apparently this sequence has all sorts of spooky occurrences in the natural world and so on.

But I'm 39 and I'm only now learning about this sequence. And here's my third grader recognizing Fibonacci numbers in an address.

Once I got over the weirdness of it all, it became rather fun. We talked Fibonacci through the rest of our walk, with me quizzing Lizzy on which was the next Fibonacci number.

We were actually out soliciting donations for Boy Scouts, and as we stood on one porch, Lizzy was dancing around the porch chanting the next Fibonacci number--377. The woman at the door asked for a suggested donation amount and Lizzy chanted her number. The woman was a bit stunned that we would ask for $377, and though I explained Lizzy was just doing math, she continued to be suspicious that I was using Lizzy to get people to donate more money.

Anyway, we got up to 987 before we stopped calculating the sequence. Impressively, Lizzy only needed to use paper and pencil for the last couple of numbers (610 and 987, I believe).

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