Mathematical stuff

If you have not seen this question before, you will probably be surprised by the answer.

What is the minimum number of randomly selected people that you need in a room, such that there is a 50 : 50 chance that 2 of them have the same birthday?

Most people's first guess is 366 divided by 2, which is 183, but that is not even close.
Press the Spoiler button for the answer, and more details

Ha! I knew the answer to that one without even clicking the spoiler tag.

I only knew it because it was in a pop science book with a chapter about statistics and probability.

Just found out today that the Roman numeral "S" represents "a half",
so SIX would equal 8½ (10 minus 1½)
S is not included in this chart, but is documented to be ½ in wikipedia.



Apparently King Louis XIV (the fourteenth) of France preferred 4 to be written IIII instead of IV,
so he had a rule that all his clocks were like that. He also preferred to be known as Louis XIIII

Interesting article about orders of magnitude and computing power

http://en.wikipedia.org/wiki/Orders_of_m...mputing%29

(20-02-2011 12:25 )TheWatcher Wrote:  I saw this amazing co-incidence in a book about pi some years ago


The value of pi has now been computed to over 1 trillion decimal places, I just showed the first 5 above.
more info at http://en.wikipedia.org/wiki/Pi

I'm going to use that ingenious maths coincidence to pick up girls lol. Thanks Watcher, top stuff, also very interesting and insightful to

Interesting article about the number 72 yesterday
http://www.bbc.co.uk/news/magazine-14217443

They were deafening when i was in Australia,but never realised Cicadas were part of a code.apparently they only appear after a prime number of years.




http://www.bbc.co.uk/news/magazine-14305667

Fascinating stuff The Watcher:

Are you watching "The Code" on BBC2 right now - think you'd love it.

MeT

I just caught the end of Dara O Briain's program (School of hard sums) on DAVE channel a couple of nights ago. They had a problem about finding the quickest route to reach an object in the middle of a river. They did not give a formula and only solved it by trial and error. I have simplified it by using unit scaling but it is basically the same problem. See diagram.

Points A, B and C lie on the waters edge. It is required to find the route that gives the shortest time between A and D, i.e the value of x for different values of k (k greater than or equal to 1, where k is the speed on land divided by the speed in water.
Obviously if k = 1, the quickest route would be a straight line from A to D.
For k = 3 say, the quickest route would be to run to point B and then swim from B to D. As k gets larger, x would increase and B would move nearer to point C.
I wrote a very simple computer program in a couple of minutes to show that this was the case, and indeed it was. e.g with k =2, x = 0.4 approx, and with k = 3, x = 0.65 approx. I wondered if there was a formula for it. This took a lot longer to solve.
Solution

The most interesting thing about this result is that the quickest route is always the straight line from A to D until k is greater than the square root of 2 (x can't go negative) Again this was confirmed by my computer results.

Quote:They had a problem about finding the quickest route to reach an object in the middle of a river.

Use a boat.