BY. Guests at a Party

February 12, 2007 · The Mathcast, math puzzles · Permalink

«« BW. The Math Factor Million Dollar Give Away!!!· · · BZ. Two Teams »»

A short, but tricky puzzle: how many guests must you invite before you can be sure that there are at least three mutual acquaintances or three mutual strangers?

 
icon for podpress   [2:08m]: Play Now | Play in Popup | Download

1 Comment »

  1. Karen Appleby said,

    June 16, 2009 at 1:46 pm

    Hi: I have only recently discovered The Math Factor on Itunes, so I am w-a-y behind the present — I’m only up to problem CA. But, I keep hearing you say, “send us an e-mail”, so I thought I would (of course I’m aware it’s possible that in the current podcasts, you don’t say that — I feel a bit like a stargazer in that what I’m hearing now left Arkansas two years ago).

    I wanted to comment on two issues: this one (Ramsey numbers) and AO — choosing balls from a bag with a 50% of pulling four blue ones. First, AO. It’s been a couple weeks since I heard that one and the answer (8 balls) has been bothering me all that time — it made absolutely no sense to me, as somehow I was thinking that the rest of the “n” balls were not blue, and I knew that there were many, many ways to not get four blue ones if half of them weren’t blue!. Twice I started to write you to see if I could get some clarification and twice I thought, “I wonder if it means “x”, and FINALLY yesterday I had enough sense to brush up on my probability theory, and experiment with various combinations. So — now I’m thinking that the answer is: 8 balls, and seven are blue. It also seems improbable to me that you need that many to approach a 50% chance of drawing four blue, but at least I have a mathematical formula that backs it up. So the point of this comment is: it was great to have a problem like that to mull over and it was great to be able to use relatively simple math to finally understand it.

    Now, on to the Ramsey numbers. When Chaim said that we didn’t know what the number was for R(5,5) but it was between 43 and 49, I thought, “how can you possibly not know the answer to a problem with such low numbers as upper and lower bounds?”. Which drove me to the web and now I know. It’s mind-blowing! So, the point of this comment is: this is why I really like the show — normally I can actually understand the mathematical issues (I have a highly deficient math background — no problem involving trigonometry or calculus need apply — occasionally I muse that people who lived 2,000 years ago knew more math than me) — and the puzzles are straightforward enough to keep all the factors in mind so I can think about them at odd moments. Many thanks to Kyle for carefully restating them every week!

    Looking forward to joining you folks in “real-time” when I catch up. Thanks for making this available to the audience beyond “Ozarks at large”.

    Karen

RSS feed for comments on this post · TrackBack URL

Leave a Comment