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Tonamel · Veteran Joined: 06 Oct 2003 Posts: 104

Well, if we're only talking about the second kid, then the probability remains 1/2. The first kid doesn't have any effect on that. Like flipping a coin, the probability on each flip remains the same no matter how many flips came beforehand.

If the question was "What is the probability that both are girls?" then the answer would be 1/4, but that doesn't seem to be the question to me.

**Posted:** Sat Jun 27, 2009 8:42 pm

vapor

**Posted:** Sat Jun 27, 2009 8:53 pm

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

True. So the question doesn't ask for the probability of the event "girl, girl", rather, it asks for the probability of the event "girl", separate from the first event?

Is that right?

**Posted:** Sat Jun 27, 2009 9:05 pm

Abraxas

I can't help, but read the question like it would say "What is the probability that both robots are girls?", because of the "also". It sounds the same to me. But I realise that almost everyone has encountered this "trick" before and that's why there may be a second "trick", like you suggest.

Is this one of the 6 pages?
Or do we have an idea what the solve will be used for?
Never mind. Laughing

12th or 14th of July, which is it?

**Posted:** Sat Jun 27, 2009 9:09 pm

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

I just can't tell. LOL.

Dunno

They're pretty close to each other, 12th and 14th, anyway. Razz

**Posted:** Sat Jun 27, 2009 9:14 pm

FriarTech

1 of 36

**Posted:** Sat Jun 27, 2009 9:24 pm

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

Re: 1 of 36

**Posted:** Sat Jun 27, 2009 9:27 pm

Abraxas

**Posted:** Sat Jun 27, 2009 9:28 pm

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

**Posted:** Sat Jun 27, 2009 9:42 pm

Abraxas

"But the substations wouldn't activate, either. Our brave warriors came back another 9 days later on the Day of the Great Reprogramming This Time For Realz. And finally did God's work, dammit."

"Unfortunately, nothing happened. Because it turns out they missed the Day of the Great Reprogramming on the 13th. And that's my dear Kid A...that's how the robots were saved! Humans are really dumb."

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

So what pages have we got so far?

**Posted:** Sat Jun 27, 2009 10:00 pm

highwind767

Between the guys in IRC, we've come up with 1/3 as another possible answer, which fits after thinking it over. Below is random probability to back it up.

In this case, there are only 4 combinations of Girl and Boy:
Boy/Girl
Boy/Boy
Girl/Boy
Girl/Girl

While this makes it seem like the final answer is out of four, it is not. The line in the image says "one of them is a Girl robot" however, which means that Boy/Boy cannot be included thanks to the lack of Girl robots, leaving us with:
Boy/Girl
Girl/Boy
Girl/Girl

Out of these, there is only a single choice in which one can be a Girl, and "the other Kid is also a girl robot" which is Girl/Girl, leaving us with a 1/3 probability.

So that's the 12th, 13th, and 14th as potential dates now. Isn't this fun? Laughing

**Posted:** Sat Jun 27, 2009 10:03 pm

Abraxas

PostLarval came up with 2/3 first. He brought us on the right track, though. But it needs to be said, because otherwise that little story up there makes no sense to anyone. Very Happy

The 36 could split up into groups of 12, now.
Or if PL comes back with the 2/3 somehow, the split still works out. So that's why they picked the 36!

hatpins · Boot Joined: 22 Aug 2008 Posts: 54 Location: Outside

http://en.wikipedia.org/wiki/Boy_or_Girl_paradox
http://mathforum.org/dr.math/faq/faq.boy.girl.html
http://mathforum.org/library/drmath/view/52186.html

Gah.

**Posted:** Sat Jun 27, 2009 10:18 pm

PostLarval

**Posted:** Sat Jun 27, 2009 11:13 pm

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