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