Numerical Coincidences

[mark_roach]

Just checked my webmaster tools account.

Web crawl errors

Pages not found : 404

Has any one else come across any similar number based coincidences ?

I suspect this thread will only appeal to the mathematicians amongst us, so any more than 1 reply would be a result.

[LifeinAsia]

Pages not found : 404

I hope you did a screen capture of that! I'd frame it and keep it above my desk. :)

This is more of a webmaster issue- I doubt many mathematicians (unless they have web developer experience) would see the humor of it.

[wheel]

I have the ability to repeatedly choose 7, 2 digit numbers between 1 and 50 that are guaranteed not to have more than one number in common with 7 government selected numbers.

[wheel]

I believe the statistical magician uses this non-intuitive 'trick'. If you've got 30 or 50 people in a room (I forget which), there's a high probability that two people will have the same birthday.

[mark_roach]

I remember doing the maths for that. I seem to remember that the 50/50 number is around 23, any more than that and it is odds on.

If anyone is interested I am sure i could dig out the formula to work it out.

[swa66]

birthday collisions are well known

30 people: ~70% chance of finding at least one collision of birthdays
50 people: ~97% chance

The counter intuitive part is in the collision itself: it's not somebody having the same birthday as you, it's finding any pair of people in a group having the same birthday (and the possible pairs increase exponentially in number)