November 23rd is Fibonacci Day! Celebrate by talking to your child about the history of this fun math holiday. Then, go on a scavenger hunt with your child to look for Fibonacci numbers – they’re all around us!

The first four Fibonacci numbers (1, 1, 2, 3) written in date form (11/23) translate to November 23, or Fibonacci Day! On this day, we celebrate all things Fibonacci, or all things in nature.

## A Little History

Leonardo Bonacci of Pisano (Fibonacci) was an Italian mathematician who lived in the middle ages. He is best known for popularizing the number system that we use today. His most famous book, *Liber Abaci*, introduced the Fibonacci numbers to the western world with a problem involving rabbits.

## Fibonacci’s Number Sequence

The sequence begins with the numbers 1, 1, 2, 3, 5, 8, 13, and continues to infinity. The numbers in the Fibonacci sequence are generated by adding the two preceding numbers. Here is how you can generate the Fibonacci sequence:

Start with 1. Add 1 to the number before it (there is no number before it, so assume 0), and add that sum to the sequence. 1 + 0 = 1, so the sequence becomes 1, 1.

Continue adding the last two numbers to determine the next number in the sequence. For example:

1 + 1 = 2, which becomes the next number in the sequence: 1, 1, 2

2 + 1 = 3, which becomes the next number in the sequence: 1, 1, 2, 3

3 + 2 = 5, which becomes the next number in the sequence: 1, 1, 2, 3, 5

5 + 3 = 8, which becomes the next number in the sequence: 1, 1, 2, 3, 5, 8

And so on! Fibonacci numbers are hiding all around us, if you open your eyes and look for them you will see them everywhere!

## Where can you find Fibonacci numbers?

- Find a nautilus shell and count the number of chambers. No matter the size of the shell or number of chambers, it will be a Fibonacci number.
- Cut an apple through its center, not through its stem. Notice the five-pointed star, another hidden Fibonacci number.
- Look for flowers and leaves. Count the petals or points. The total will always be a Fibonacci number!
- Have you ever wondered why four-leaf clovers are so rare? They don’t happen often in nature because four is not a Fibonacci number!
- Look at a piano keyboard. How many keys are in an octave? How many white keys? How many black keys? Music is filled with examples of Fibonacci numbers! Watch Music From the Fibonacci Sequence to see for yourself.