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-   -   Raffle odds (https://www.askmehelpdesk.com/showthread.php?t=328602)

  • Mar 12, 2009, 11:00 PM
    gtravis541
    Raffle odds
    I guess I'm thinking too hard. If there is one prize and 300 tiks my odds would be 1 in 300 . If 1 prize and 600 tickets and I buy two, I'm told my odds are the same.

    My question is why is the odds the same ?
    If 1 out of 300 I could pull 299 before getting to my #.
    If 2 of 600 the I could pull 598 before getting to my #.
    It just seems that would mean my odds are worse?
  • Mar 16, 2009, 12:11 PM
    ebaines

    Please do not start a new thread if you are asking a follow up to a previous question - this makes it difficult for others to follow along.

    The original question is here:
    https://www.askmehelpdesk.com/mathem...ce-328086.html

    One way to look at this is to consider the odds of not winning. Given 300 tickets and exactly 1 winner, if you buy one tiket the chance of you not having the winning ticket is 299/300 - that's because if any of the other 299 tickets win then that means you lose. Do you see why that is? Now consider the case where there are 600 tickets, 1 winner among them, and you have bought two tickets -- the odds of you not winning is 598/600, (if any of the other 598 ticktes win, then you lose). So for both cases the odds of you losing are the same. Hence the odds for you winnng are the same.

    As for your conjecture about the possibility of pulling 598 tickets before you might win - true enough; however, this is getting at a completely different issue. If you calculate the expected number of raffle tickets that would be pulled before you win, then you would find that on average it takes more draws to win when you have 2 out of 600 than it does when you have 1 out of 300. Specifically, if you have 1 out of 300 on average it would take 150 draws before you win. If you have 2 tickets out of 600 then on aveage it would take around 175 draws before you would have a winner. I can show you the math, but won't clutter this tread with it unless you want, because that's not the game you're playing.

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