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MathGroup Archive 2011

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Re: count zeros in a number

  • To: mathgroup at smc.vnet.net
  • Subject: [mg121799] Re: count zeros in a number
  • From: Ulrich Arndt <ulrich.arndt at data2knowledge.de>
  • Date: Mon, 3 Oct 2011 04:21:00 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201110020636.CAA28027@smc.vnet.net>

one way is to convert the number to a string and count the "0" at the end

a = 24^24*55^55
StringLength[
  StringCases[ToString[a], 
   Longest[x : "0" ... ~~ EndOfString] -> x]][[1]]
a = 123
StringLength[
  StringCases[ToString[a], 
   Longest[x : "0" ... ~~ EndOfString] -> x]][[1]]
a = 1230
StringLength[
  StringCases[ToString[a], 
   Longest[x : "0" ... ~~ EndOfString] -> x]][[1]]

Ulrich

Am 02.10.2011 um 08:36 schrieb dimitris:

> Hello.
> 
> Consider e.g. the number 24^24*55^55.
> This number ends with exactly 55 zeros as the following demonstrate
> 
> In[201]:= Mod[24^24*55^55, 10^55]
> Mod[24^24*55^55, 10^56]
> 
> Out[201]= 0
> Out[202]= 20000000000000000000000000000000000000000000000000000000
> 
> 
> What I want now is a way to count the zeros that a number ends without
> knowing in advance this number of zeros like in the above example.
> 
> Thanks in advance.
> Dimitris
> 





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