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MathGroup Archive 2000

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Selecting numbers with all odd digits

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22170] Selecting numbers with all odd digits
  • From: "Tom De Vries" <tdevries at shop.westworld.ca>
  • Date: Thu, 17 Feb 2000 01:23:59 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello all,

In one of the math classes I am teaching we are doing some work with
permutations and combinations.  One question in the text was,  "how many
positive integers less than 700 have all odd digits?"

I had done the question "by hand" and then wondered how to use Mathematica
to demonstrate that the solution was the correct one.

I am still very far down on the learning curve in most things, but I managed
to bludgeon my way to an answer  (thankfully the same as mine!)

Select[

  Range[699],

  Union[ OddQ [ IntegerDigits[#]]] == {True} &

  ]

I am sure my trial and error method can be improved upon.  I am not talking
speed as much as simply using Mathematica in a way that makes sense and
would be more logical??

Thanks for any suggestions might have!

Tom De Vries
Edmonton, Alberta
Canada



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