Math CentralQuandaries & Queries


Question from Serena, a student:
How many times is 9 in pi?


I presume you don't mean "what is pi/9",(the answer to which is about 0.349) but "how many times does the digit 9 appear in the decimal expansion of pi?"

The answer is that we do not know.

On the one hand, it is probably true that any mathematician in the world would bet a year's pay against a cup of coffee that the answer is that it appears infinitely often. Many billion digits have been computed and no digit appears to predominate or appear unusually often. It is generally believed that pi is "normal" in any base - that is, all digits appear in equal proportions.

However, we have no mathematical theory at the moment that comes close to answering such questions!



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