Answer:
The Golden ratio, phi
Explanation:
A fibonacci series is one in which the next term is equal to the sum of the previous two terms.
0,1,1,2,3,5,8..
When you take the ratio of these terms:
3/2 = 1.5
5/3 = 1.666666667
8/5 = 1.6
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As you increase the no. of terms, you'll observe that this ratio approaches 1.618 (ph, The Golden ratio)