Raheel Khan
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 Mar 9 comment Determine if a positive integer $x$ is a product of a power of 2 and a power of 5. $f(x) = 2^n \cdot 5^n$ MichaelHardy: Thank you. These edits are very helpful in learning/using Latex. Mar 9 accepted Determine whether the decimal expansion of a rational number is infinite Mar 9 comment Determine if a positive integer $x$ is a product of a power of 2 and a power of 5. $f(x) = 2^n \cdot 5^n$ Can I also assume the inverse? That is if $x$ in base 10 has a minimum of or exactly $min(m,n)$ trailing zeros, then $x$ is definitely a product of $2^m5^n$? Mar 9 revised Determine if a positive integer $x$ is a product of a power of 2 and a power of 5. $f(x) = 2^n \cdot 5^n$ added 86 characters in body Mar 9 comment Determine if a positive integer $x$ is a product of a power of 2 and a power of 5. $f(x) = 2^n \cdot 5^n$ Thanks for pointing that out. Editing the question to reflect them being NOT the same. Mar 9 comment Determine whether the decimal expansion of a rational number is infinite Thank you for that explanation. On a related note, here is question about decimal/binary representation of such numbers if you are interested. Mar 9 asked Determine if a positive integer $x$ is a product of a power of 2 and a power of 5. $f(x) = 2^n \cdot 5^n$ Mar 9 comment Determine whether the decimal expansion of a rational number is infinite @GerryMyerson: Thanks. Just to confirm, testing the denominator to be a power of 2 or 5 OR like you said a product of a power of 2 and a power of 5. Now I'm wondering if I would have to iterate to test this (similar to how we find factors of large numbers). Or is determining the same possible with a single calculation? Please let me know if you feel this should be posted as a new question. Mar 9 revised Determine whether the decimal expansion of a rational number is infinite Changed irrational to rational. Mar 9 comment Determine whether the decimal expansion of a rational number is infinite Thanks. I had the terminology incorrect. Yes I am referring to rational numbers (where the decimal part is infinitely repeating such as $1/3$). So for base 10, any fraction whose denominator is not a power of 2 or 5, would produce a never-ending sequence of digits after the decimal. Am I understanding that correctly? Mar 9 asked Determine whether the decimal expansion of a rational number is infinite Jan 21 awarded Nice Question Oct 20 awarded Notable Question Jul 3 comment Amplitude versus time producing unexpected patterns. @Henning, could you please elaborate on the last paragraph. I'm assuming you are only referring to the visual representation of the data. Jul 2 awarded Curious Mar 8 awarded Autobiographer Feb 4 accepted Finding $n$ in $n=ReverseFactorial(x)$ where $x$ is known. Jan 25 comment Finding $n$ in $n=ReverseFactorial(x)$ where $x$ is known. @Amzoti: Ouch. I can see what you mean. My case is closer to $101!-100!$. But instead of performing the actual calculation, I wonder if there is some logarithmic scale where I can approximate which two values of $n$ a given number falls between. Jan 25 revised Finding $n$ in $n=ReverseFactorial(x)$ where $x$ is known. added 334 characters in body Jan 25 asked Finding $n$ in $n=ReverseFactorial(x)$ where $x$ is known.