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One of the greatest mathematicians of the Middle Ages was Leonardo of Pisa. He was born in A.D. 1175 in Pisa, Italy, and became known as Fibonacci. Fibonacci wrote a book on doing math in the decimal system. In his work with numbers, he became fascinated with a problem involving rabbits. He posed this problem to those who wanted to practice their math:
A pair of rabbits is put in a field. If the rabbits take a month to become mature and then produce a new pair every month after that, how many pairs will there be in twelve months? (Assume that the rabbits continue to bear young and that each pair produced will consist of one male and one female.)
Fibonacci looked at the answer to this problem and discovered an interesting number sequence. The sequence begins 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, ... and continues. The numbers in the sequence are called Fibonacci numbers. Did you notice the pattern at work here? Each number, except for the first two, is the sum of the preceding two numbers. Fibonacci also found that dividing each number in this sequence by the one that precedes it produces a ratio of about 1.618034. This number is known as the golden ratio.
What's really interesting is the evidence of Fibonacci numbers and the golden ratio throughout nature. Think about a pinecone, for example. Its "petals" spiral around in two directions. The number of petals it takes to go once around the pinecone is almost always a Fibonacci number! Other plants exhibit Fibonacci numbers, too. The leaf arrangements of elm, oak, holly, and pear trees, among many others, are in Fibonacci numbers. Scientists say that the 1.618 leaves per turn on plant stems give the plant the best possible exposure to sunlight and to insects for pollination. Some scientists even claim that the reason why four-leaf clovers are so rare is because four is not a Fibonacci number! You can find lots of examples of Fibonacci numbers in nature, in everything from seashells to animals.
Humans have some Fibonacci tendencies as well. Look at your hand. You have two hands, each with five fingers. Each finger has three parts and two knuckles. Is this an example of a natural wonder or a mathematical coincidence? You be the judge.
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