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Lateral Thinking - Preconceptions

Sun May 11, 2008 2:33 am  by xfx

I'm going to flip a coin four times.

The first time the coin shows heads.
The second time, the coin shows heads again.
And so does the third time.

What are the odds that flipping the coin a fourth time will show tails?
Mon Jun 09, 2008 12:56 pm  by steinjim

Three consecutive heads is not enough to judge as to the fairness of the coin, so we'll assume that it is a fair coin (if you had flipped 100 consecutive heads, then you could certainly assume that it is not a fair coin).

That given, the [u]probability[/u] of a tail is 1/2, or 50%. If you really want [u]odds[/u], then the odds of a tail is 1:1 , which is P(tail) / P(head)
Fri Jun 26, 2009 4:03 pm  by Hahaveryfunny:3

1/2 50% Half. It only relies on the prob of landing on side 1 or side 2, it dosnt matter the past flips. Its based on luck.
Tue Jun 30, 2009 7:33 pm  by xfx

That's absolutely correct Hahaveryfunny:3
Wed Feb 02, 2011 4:35 am  by gyinagal

The answer would appear to be 15/16, because the chances of it being heads again is 1/16, but its actually 1/2 because the probability of one side does not affect the probability of the other.
Wed Feb 02, 2011 5:43 am  by xfx

Hahaveryfunny:3 had it right -- every other answer/assumption is wrong
Tue Jan 29, 2013 6:09 pm  by Akoito

50/50 of course
Thu Sep 12, 2013 5:40 am  by zozee

50/50, doesn't matter what happened on the last three goes
Tue Oct 22, 2013 11:30 am  by kotrakesh

as it is not mentioned its a non biased coin
Sat Nov 02, 2013 4:30 am  by V7Theory

yellow, because ice cream doesn't have any bones.
Fri Nov 15, 2013 4:54 am  by ValhallaStarfire

This, I do not know. The odds on a standard coin would be near 1:1 leaning in favor of heads for slightly less gravity and there is also the VERY slim chance that the coin lands on its side. (I'd like to see that happen.)
But there is still the possibility that the coin is a double-header.
Wed Feb 05, 2014 3:04 am  by Nsj

The probabilty is 100%. It's the same as throwing a knife. If you grab it by the handle it will hit with the handle. This is also the reason why in a coin game you aren't allowed to see the coin before betting.
Wed Jun 10, 2015 9:53 pm  by oncemoreforluck

it's 50/50 or 50%. both sides are possible until the coin lands.

just because the coin was landing on heads each time before that, it doesn't mean anything.


if this coin is weighted, then the chance of it landing on tails is 0%.
Tue Aug 16, 2016 6:52 am  by tjn50351

The coin has demonstrated a propensity to show heads. Therefore I believe answer to the question is the odds of tails on the fourth flip is strictly less than 50%. But after only 3 flips its damn near 50%.
Thu May 31, 2018 6:07 pm  by bedead

50 percent
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