Re: Is this a combinatoric problem?

mowsen@xxxxxxxxxxxxxx wrote:
Dear Group,


i''m totally confused about the following problem:

i've got a 1-10 length digit which is sorted in descending order:

i.e.> 9876543210 is (the only btw.) possibillity for a 10 length
number.

i'll use a five digit for easier overview:

98765, 98764, 93210, 64310 would all be possibilities.
98766 is not a possibility, because every digit right must be smaller
than that to the left (descending order).
so the last possibility for a five digit is: 43210

so my question is: can the number of possibilities be solved within
combinatoric aspects?
the problem is, that the possibilities for the righter digits depend
on the digits to the left.

does anyone see a solution here?

You want to know in how many ways you can choose 5 elements
out of 10. This is indeed a "combinatoric aspect":

C(10,5) = (10*9*8*7*6)/(1*2*3*4*5) = 252

See for example
http://en.wikipedia.org/wiki/Combinatorics
and especially the reference to "combinations without repetitions":
http://en.wikipedia.org/wiki/Combinations.

(The "descending order" simply ensures that you count each combination
only once.)

Cheers,
Rainer Rosenthal
r.rosenthal@xxxxxx
.

Relevant Pages

  • Ordering Results
    ... then by the 2 digit numbers in ascending order. ... then by the 2 digit numbers in descending order. ... If I could use a case statement within the order by clause, ...
    (microsoft.public.sqlserver.mseq)
  • Re: Ordering Results
    ... then by the 2 digit numbers in ascending order. ... then by the 2 digit numbers in descending order. ... If I could use a case statement within the order by clause, ...
    (microsoft.public.sqlserver.mseq)
  • Re: Is this a combinatoric problem?
    ... i've got a 1-10 length digit which is sorted in descending order: ... Which happens to be the Zip Code for Ohio State University. ... Gerry Myerson ...
    (sci.math)
  • Re: Is this a combinatoric problem?
    ... i've got a 1-10 length digit which is sorted in descending order: ... digit solutions and 120 seven digit solutions. ... Do the bigger left hand digits first, ...
    (sci.math)
  • Re: create reference number based on old one...
    ... "Armin Zingler" wrote in message ... I'm trying to create a function that will create a "reference number" ... which is the year followed by a 6 figur digit "000100" ... I now understand your interpretation. ...
    (microsoft.public.dotnet.languages.vb)