# What is special about Fibonacci number? #34

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opened this Issue Feb 7, 2014 · 5 comments

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### shankardevy commented Feb 7, 2014

 Under "Size and Value" It is mentioned that: "Both size and value should be a Fibonacci number." There is just a link to Fibonacci number in Wikipedia without explaining why a number not in fibonacci series won't work? I read North guide and it's fantastic but I am wondering what relevance does Fibonacci number have in relation to project management and sizing the story? Would you please add a brief explaining the importance? I hope this would help many like to me to understand the concept better. Thanks
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### Snugug commented Feb 11, 2014

 Fibonacci numbers are good for use when sizing as they are a well known, non-sequential inter sequence that grows in such a way to give meaningful differentiations between a number and that which came before it. It's also easy to visualize the relative difference between two numbers quickly. For instance, if we were to use a 1-10 scale, the difference between 6 and 7 doesn't seem so large; 7 is only one more than 6. But when using Fibonacci numbers, the difference between 13 and 21 is large enough that it's easy to visualize either how much more important the 21 is when compared to the 13, or how much more work/risk it has (depending on the context). Hope that helps

### shankardevy commented Feb 15, 2014

 thank you. This line "to visualize the relative difference between two numbers quickly" helps me understand the concept much better. Would you think a brief description as given in your answer deserves a place in the guide?
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### joshcarr commented Feb 17, 2014

 The answer on this Stack Overflow question is also interesting: Out of the first six numbers of the Fibonacci sequence, four are prime. This limits the possibilities to break down a task equally into smaller tasks to have multiple people work on it in parallel. Doing so could lead to the misconception that the speed of a task could scale proportionally with the number of people working on it. The 2^n series is most vulnerable to such a problem. The Fibonacci sequence in fact forces one to re-estimate the smaller tasks one by one. http://stackoverflow.com/a/9377005/908769
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### Snugug commented Feb 17, 2014

 I like that answer better. When I go to update North I'll include that. On Feb 17, 2014, at 1:32 PM, Josh Carr notifications@github.com wrote: The answer on this Stack Overflow question is also interesting: Out of the first six numbers of the Fibonacci sequence, four are prime. This limits the possibilities to break down a task equally into smaller tasks to have multiple people work on it in parallel. Doing so could lead to the misconception that the speed of a task could scale proportionally with the number of people working on it. The 2^n series is most vulnerable to such a problem. The Fibonacci sequence in fact forces one to re-estimate the smaller tasks one by one. http://stackoverflow.com/a/9377005/908769 — Reply to this email directly or view it on GitHub.