If you're not paying me to type a certain way, either FUCK OFF or do a search/replace (or both). I owe you nothing. If you are paying me, and putting only a single space is a job requirement (this has never happened), then I'll do a search/replace when I'm done typing. Then I'll look for a better job. If HTML doesn't render the spaces -- fuck it, not my problem. If you enjoy typing a single space -- I don't give a fuck what you do just like you shouldn't give a fuck what I do.

Please see this -- this is a well-known puzzle over 50 years old, and I'm surprised that there are people on Slashdot who weren't familiar with it already.

I'm not sure why I'm wasting time responding to a troll but whatever.

> The question is 1 coin is heads, what is the probability that the other coin is heads. In other words, your girlfriend is pregnant. What are the odds that my girlfriend is also pregnant?

No, you read it wrong. What it's actually asking is (if we pretend all girlfriends have exactly a 50% chance of being pregnant): "two girlfriends exist. At least one of the two is pregnant. What are the odds that both girlfriends are pregnant?"

You just read it wrong and you're too stubborn too admit that you could ever be wrong, even though this puzzle is FIFTY YEARS OLD and is well documented all over the internet. Just see the Wikipedia article on it.

Unfortunately, I have some bad news for you -- this is actually a well-documented mathematical puzzle, and there's even a Wikipedia article on it.

Similar to the Monty Hall Problem, almost everybody assumes 50% at first, since it seems natural and intuitive. When the question is stated unambiguously (the version at the top of this thread was admittedly not very clear), the answer really is 33%, provable both by basic math and by actual testing. The purpose of the problem is to see if someone can admit that he's wrong when he's confronted with logical and empirical evidence. This is often used during job interviews. Needless to say, you wouldn't be getting the job.

See also Bertrand's Box Paradox or the Three Prisoners Problem for similar puzzles.

I think I can help clarify this for you since you seem to be the only one to still be having trouble understanding this.

Two coins are flipped. In the absence of any other information, there are four possibilities:

Heads, Heads: 25%
Heads, Tails: 25%
Tails, Heads: 25%
Tails, Tails: 25%

Then we receive some new information: at least one of the coins is Heads. That rules out the last option. Let's recalculate the odds based on the new information:

Heads, Heads: 33.3%
Heads, Tails: 33.3%
Tails, Heads: 33.3%

Now, let's look at the question (reworded slightly to hopefully make it less confusing for you): "Two coins are flipped. At least one of the two coins lands Heads. What are the odds that both coins landed Heads?"

In the first instance (33.3%), both coins landed heads. In the second and third instances (combined 66.7%), both coins did not land heads.

So the answer is 1/3 (33.333...%)

You can verify this with some actual coins. Flip two coins, then if either coin is heads, check to see if the other coin is heads. Keep a tally of how often the other coin is or isn't heads. If you haven't actually flipped coins, you're just talking out your buttocks.

I don't know how else to help you if you're still struggling.

I am on my side pretty sick of getting nearly killed once per year

If you find yourself in near-accidents this frequently, the bad driver is probably you.