August 2007 - mathfun@mailman.xmission.com

[math-fun] I've added you as a friend on Doostang...
by Andrew Latto 09 Aug '07

09 Aug '07

I've requested to add you as a friend on Doostang, an invite-only career community started at Harvard, Stanford, and MIT. You can use Doostang to find a job or internship, network, and access valuable career information from peers and industry professionals. Thanks, Andrew Follow this link to accept my friend request. http://www.doostang.com/sign_up2.asp?fid=&invite=FF9030BC-ADBB-40A9-8344-DD… Doostang members have successfully received offers from: Goldman Sachs, Facebook, HBO, McKinsey, Google, Apple, Bill and Melinda Gates Foundation, Draper Fisher Jurveston, Saatchi & Saatchi, NBC, Morgan Stanley, Chanel, Summit Partners, U.S. Congress, Conde Nast, Nike, D.E. Shaw, World Bank, and hundreds more...

1 0

[math-fun] Puzzle
by Eric Angelini 08 Aug '07

08 Aug '07

Hello, Have fun (?) http://www.cetteadressecomportecinquantesignes.com/DaDoRunRun.htm Best, É.

1 0

Re: [math-fun] How we
by Dan Asimov 08 Aug '07

08 Aug '07

I, too, came upon the idea of using moving coordinate frames fairly soon, perhaps based on a mental picture.* Not having thought about relative motion for a decade prior, I'm sure it's because I'm currently reading the recent biography of Einstein (by Walter Isaacson). (Has anyone else read that book? I've had at least one interesting matematical idea as a result of reading it.) --Dan _____________________________________________________________________ * What I posted was what I wrote on paper (including no pictures). ----------------------------------------------------------------------- Bill T. wrote: << On Aug 6, 2007, at 7:57 AM, gale(a)Math.Berkeley.EDU wrote: > I'M AFRAID I didn't express myself clearly.I wasn't asking for a > solution > but rather about the mechanics of finding it. Did either of you > use pen > or pencil or paper at any point? I had to draw two pictures before > I could > see what the equations had to be. Maybe you were able to do all these > things in your head in which case my speculations are off base. > . . . . . . In my case, I worked it out in my head. I had a mental picture of the two people running in opposite directions around a circle, and then I thought of using moving coordinates as in high school physics class so that one of the runners moved at the sum of speeds, which I said to myself was one lap per minute. The same picture said the difference of speeds was 1 lap per hour. Then I thought of a picture of an interval of length 60, with two points (the two speeds) averaging at the halfway mark but being 1/60th apart: from the picture you see the ratio as 61:59. . . . . . . >>

1 0

RE : RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4
by Eric Angelini 07 Aug '07

07 Aug '07

... Sorry, this msg was intended for Neil only... ________________________________ De: math-fun-bounces+eric.angelini=kntv.be(a)mailman.xmission.com de la part de Eric Angelini Date: mer. 08/08/2007 00:20 À: njas(a)research.att.com; math-fun Objet : RE : RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4 > "This person" is of course my old friend and long-time > collaborator Ron Hardin (...) ... Thanks for the info, Neil !

1 0

RE : RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4
by Eric Angelini 07 Aug '07

07 Aug '07

> "This person" is of course my old friend and long-time > collaborator Ron Hardin (...) ... Thanks for the info, Neil ! I love his website (which I know for a long time) Best, E. (I'm browsing the OEIS for a 16000 signs article I have to send to "Pour la Science" -- a special "puzzle" issue in mid-october; topic: < Fun with Sequences >! I have to produce a dozen problems related to seq.) I start my piece like this: > Le site de Neil Sloane, « The On-Line Encyclopedia of Integer Sequences » recense plus de 130000 suites de nombres entiers, un vrai trésor ! Il y a la suite des nombres pairs, celle des nombres premiers, celle de Fibonacci, celle des manières d'obtenir certains tirages au poker, celle des « Cake numbers » (les parts de gâteau que déterminent n coups de couteau), celle des opus des symphonies de Beethoven, etc. I'll send you the definitive .pdf in september Best, E. -------------- ________________________________ De: math-fun-bounces+eric.angelini=kntv.be(a)mailman.xmission.com de la part de N. J. A. Sloane Date: mar. 07/08/2007 23:53 À: math-fun(a)mailman.xmission.com; math-fun; math-fun Cc: njas(a)research.att.com Objet : Re: RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4 > This person http://home.att.net/~rhhardin/selfref.html <http://home.att.net/~rhhardin/selfref.html> <http://home.att.net/~rhh > ardin/selfref.html> > has...compiled? computed? exhaustive sets of self-describing > sentences of various forms "This person" is of course my old friend and long-time collaborator Ron Hardin, rhh, who has contributed many sequences to the OEIS. Neil _______________________________________________ math-fun mailing list math-fun(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun <http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun>

1 0

Re: RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4
by N. J. A. Sloane 07 Aug '07

07 Aug '07

> This person http://home.att.net/~rhhardin/selfref.html <http://home.att.net/~rhh > ardin/selfref.html> > has...compiled? computed? exhaustive sets of self-describing > sentences of various forms "This person" is of course my old friend and long-time collaborator Ron Hardin, rhh, who has contributed many sequences to the OEIS. Neil

1 0

RE : [math-fun] Re: math-fun Digest, Vol 54, Issue 4
by Eric Angelini 07 Aug '07

07 Aug '07

Thanks, Steve ! Best, E. ________________________________ De: math-fun-bounces+eric.angelini=kntv.be(a)mailman.xmission.com de la part de Steve Witham Date: mar. 07/08/2007 19:41 À: math-fun(a)mailman.xmission.com Objet : [math-fun] Re: math-fun Digest, Vol 54, Issue 4 >From: "Eric Angelini" <Eric.Angelini(a)kntv.be> > >ZERO >ONE E ONE O ONE R ONE Z >FIVE E FOUR N FIVE O ONE R ONE Z >FIVE E THREE F TWO I THREE N FOUR O TWO R ONE U TWO V ONE Z >... > >Any loop or fixed point? This person http://home.att.net/~rhhardin/selfref.html <http://home.att.net/~rhhardin/selfref.html> has...compiled? computed? exhaustive sets of self-describing sentences of various forms, like, "This sentence has three a's, two c's, two d's, nineteen e's, six f's, two g's, five h's, ten i's, two l's, twelve n's, nine o's, five r's, twenty six s's, sixteen t's, four u's, four v's, eight w's, four x's, and two y's." There aren't very many. 18 of that form, for instance. (I guess he considers it cheating to add, e.g., "one q".) --Steve _______________________________________________ math-fun mailing list math-fun(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun <http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun>

1 0

[math-fun] Re: math-fun Digest, Vol 54, Issue 4
by Steve Witham 07 Aug '07

07 Aug '07

>From: "Eric Angelini" <Eric.Angelini(a)kntv.be> > >ZERO >ONE E ONE O ONE R ONE Z >FIVE E FOUR N FIVE O ONE R ONE Z >FIVE E THREE F TWO I THREE N FOUR O TWO R ONE U TWO V ONE Z >... > >Any loop or fixed point? This person http://home.att.net/~rhhardin/selfref.html has...compiled? computed? exhaustive sets of self-describing sentences of various forms, like, "This sentence has three a's, two c's, two d's, nineteen e's, six f's, two g's, five h's, ten i's, two l's, twelve n's, nine o's, five r's, twenty six s's, sixteen t's, four u's, four v's, eight w's, four x's, and two y's." There aren't very many. 18 of that form, for instance. (I guess he considers it cheating to add, e.g., "one q".) --Steve

1 0

[math-fun] Counting the letters of the line before
by Eric Angelini 07 Aug '07

07 Aug '07

Hello MathFun, has someone computed this already? (same method as A005151) http://www.research.att.com/~njas/sequences/A005151 ZERO ONE E ONE O ONE R ONE Z FIVE E FOUR N FIVE O ONE R ONE Z FIVE E THREE F TWO I THREE N FOUR O TWO R ONE U TWO V ONE Z ... Any loop or fixed point? Best, É.

1 0

RE: [math-fun] How we "do mathematics" / Marathon drinks
by Henry Baker 06 Aug '07

06 Aug '07

There are Death Valley marathons, and there are Death Valley marathons. "Badwater" is held in July & requires a good deal more than 3,5, or even 8 liters of water. One person was disqualified a few years ago for having another person run alongside & constantly spray the competitor with water! http://www.badwater.com/training/gear.html The "normal" Death Valley marathons take 3-5 hours & still require 2-4 liters PER HOUR. http://envirosports.com/events/displayevent.php?eventid=2102 http://www.envirosports.com/events/event.php?eventid=2106 I would imagine that the competitors of any of these events have plenty of time to work out the answer, but may not be "compos mentos" enough ("compos mentos" is an old Latin phrase meaning "capable of mixing Mentos with Diet Coke"). :-) At 07:24 AM 8/6/2007, Eric Angelini wrote: >> lots of math contest experience and high school teaching (...) > >A (very) old one I like : > >Two Death Valley marathonians friends complete their run >together and seek shadow in their tent nearby the finish >line. > >The first one had prepared a fresh 5-liter tank of water >in a cooling box and his friend a similar 3-liter one. > >They were about to start drinking when a journalist enters >the tent desperately asking for water. > >OK, the water is divided into three equal parts -- and drunk. > >The thankful journalist insists to pay his share and leaves >8 dollars to be split between the two friends. > >How? > >---- > >(...) and high school teaching experience, do this kind of > stuff in our heads

1 0