Re: number theory
- To: mathgroup@smc.vnet.net
- Subject: [mg12543] Re: [mg12491] number theory
- From: "Jrgen Tischer" <jtischer@pitagoras.univalle.edu.co>
- Date: Sat, 23 May 1998 18:11:07 -0400
Hi Thomas,
In[26]:= Select[Range[65],MemberQ[20 {1,2,3,4},#]&]
Out[26]= {20,40,60}
Jrgen
-----Original Message-----
From: Thomas A. Rice <trice@earthlink.net> To: mathgroup@smc.vnet.net
Subject: [mg12543] [mg12491] number theory
>I have been trying to use Mathematica to get integer solutions to
>problems, but am beating my head against the wall.
>
>Can one use Mathematica to give an exact solution in a situation like
>the following?
>
>An automobile travels at a speed exactly 20 times faster than John can
>walk, but less than 65 mph. John walks exactly at a whole number speed
>(integer) between 1 and 4 mph (1, 2, 3, or 4 mph). What are the speeds
>the car might travel?
>
>Answer: 20, 40, or 60 mph.
>
>It doesn't work for me to enter:
>
>Solve[{IntegerPart[walking] * 20 == driving, walking >0, walking < 5,
>driving < 66}, driving]
>
>I would be greatly indebted if someone could tell me if or how this
>problem can be solved with Mathematica.
>
>