Comments on: Thinking lazily about problem-solving methods

By: JP

JP — Tue, 21 Oct 2008 14:29:16 +0000

FND: Hint as requested. Part (b) asks for proof that no AP of 11 or more primes as terms can exist between 1 and 20000. 11 or more terms means 10 or more “constant differences”. If you could prove that the minimum constant difference required in such a series, when multiplied by ten, exceeded 20,000, then you would solve part (b).

So the solution (to both problems) lies in understanding what kind of characteristics the constant difference needs to have, then working out how to determine what it could be.

By: FND

FND — Tue, 21 Oct 2008 14:17:46 +0000

That blag post is still annoying me today – I’m not much of a fan of unsolvable mysteries…

As for the arithmetical progression of primes, I must admit I haven’t quite figured that out yet. A hint maybe, before I resort to invoking Google…
Kinda reminded me of the 8 ball problem though…

By: Blob » Burma Shave

Blob » Burma Shave — Tue, 21 Oct 2008 05:11:31 +0000

[...] read the xkcd comic strip, I receive it through my rss reader, ever sinceI think my friend JP wrote something about it. Now, I’ll admit that sometimes I just don’t get it. Sometimes I think it’s [...]

By: JP

JP — Fri, 16 May 2008 10:49:00 +0000

Andrew, loved the truck!

Benoit, there are many questions you ask that I have no answer to: number of readers, what they are interested in, etc.

What I can say is this. I came across the problem while at school, probably in a “mathematical olympiad” paper the teacher had circulated around the class. It did not form part of the curriculum per se, but for sure we were encouraged to study number theory, and primes within that.

[incidentally, the school in Calcutta was run primarily by Belgian (!) Jesuit priests in those days.]

I am not a mathematician; while I studied maths at school (and within my economics and statistics courses at university), all I can say is that I’ve had a lifelong interest in primes.

I have no idea what this reveals about people who ask or answer such questions.

So why did I share it? I found it elegant, beautiful, fascinating. And I like sharing things that I find elegant, beautiful, fascinating. And people seem to come back and read more…..

By: Benoît Tuerlinckx

Benoît Tuerlinckx — Fri, 16 May 2008 10:11:33 +0000

An arithmetical progression of primes!
I did not expect to see that topic appear in this blog, and it makes me wonder:

1- what percentage of the readers of this blog are able to solve it? (I must admit I only discovered half the answer i.e. 210 before googling it)

2- what percentage of the readers of this blog are interested in number theory vs the global blogger population?

3- in what context did JP hear about this problem? Was this part of his curriculum?
If so, is number theory widely taught in some regions of the world or is JP a mathematician or is Belgium an exception?

4- what does this test reveal about those who pass it — or those who ask it? It reminds me of a (much simpler) question that was traditionally asked in my company during the hiring interviews: what is the mass of the earth (give or take a factor 10), which led into sub-questions when the candidate was solving it; the one I remember is “why is the diameter 12000 and some kilometer?” (answer: by definition of the meter, which was 1:10,000,000 of a meridien)

So this entry probably tells a lot about JP and his readers, but I do not know what…

By: Andrew Yeomans

Andrew Yeomans — Wed, 14 May 2008 14:35:30 +0000

Bur beware the truck: http://xkcd.com/356/ :-)