Re: Infinity and chances of chosing something.



conkersack@xxxxxxxxx wrote:
> Hello,
>
> If a hotel has an infinate number of rooms which weren't numbered, and
> you had to guess which room was yours, what would the odds be of
> getting it right first time?
>
> If it's one in infinity of getting it right but also one in infinity of
> getting it wrong,

Why would it be 1 in infinity of getting it wrong? How many rooms
aren't yours? Infinity - 1. It would be infinity-1 in infinity.

Try simplifying the problem a bit.

What are the odds of drawing the Ace of Spades from a shuffled deck
of cards? Only 1 card is the AoS out of 52 total, so odds are 1:52.
But there are 51 cards that are NOT the AoS, so odds of drawing one
of them is 51:52.

> surely that is the same as a straight 50/50 split?

Nope. infinity-1:infinity is not the same as 1:infinity.

>
> So I'd only have to try two doors and one would be my room?

Try it with a deck of cards. Will you always find the AoS on 2 draws?
Do you see why?

>
> I really don't know anything about maths other than how to work out my
> change due at a checkout, so please be gentle!

Probability is the ratio of successful outcomes to total outcomes.

If "my room" is the success then odds are 1:infinity.
If "not my room" is the success, then odds are inifity-1:infinity.

>
> Thanks in adavance for any help/ridicule,
>
> Roger Melly.

.