The boy-girl puzzle

THe problem is smee you’re looking at the end result. Consider the possible ways of getting there, hence my awesome road/town analogy. THEY ARE NOT THE SAME

Ok then Mike. Boy/Girl and Girl/Boy – remove the ages of them and what is the difference?

There is no difference but there is a 50% of it being a girl/boy boy/girl combination compared to a 25% chance of a girl/girl combination, although I assume this attempted explanation will fail

Smee: if you really are serious (which I doubt) then lets do away with all those confusing formulae and look at the raw empirical data in my fabulous spreadsheet.

Take each row in turn, ask yourself “Does this row contain at least one girl?”
If it does then scratch a tally mark into the wall of your cell (or ask your therapist for a crayon).
Next ask yourself “Does this row contain one girl and one boy?”
If it does then scratch a mark into a different wall.

Once you have done this for all 100 rows you should find that your first wall has a a total of around 75. And the second wall has a total of around 50.

Now ask one of your carers to tell you what 50 out of 75 is as a percentage…

If there is no difference then they are the same. Why would you give one option double the chance of being the correct outcome?

Okay then… take 3 families

Family A has an older boy and younger girl
Family B has an older girl and younger boy
Family C has two girls

If you pick a family at random, what are the chances that you will pick a family with a boy?

If you believe you can discount either family A or family B from this, as you seem to be doing in your examples above, can you give a reason for which family you would discard, and why that one and not the other.

He must be trolling, this is pretty basic stuff.

Ok then Mike. Boy/Girl and Girl/Boy – remove the ages of them and what is the difference?

They are two separate ‘routes’ to having two children, where one is a boy and one is a girl. That’s twice as many ‘routes’ as there are for having two children who are both girls.

How about:
Family A has one boy and one girl, or one girl and one boy if you prefer – they only have two kids so they can’t have both.
Family B has two girls.

All permutations taken into account.

50:50

How about “djglover is correct” as a solution?

What about if they had a ladyboy?

Smee earlier:

Nope.

Smee.. if B/G is the same as G/B as you claim, and the chances of it occuring are not doubled, then you have either:-

B/B 25%
B/G or G/B 25%
G/G 25%

Which does not total 100%, or:-

B/B 33.3%
B/G or G/B 33.3%
G/G 33.3%

Which does equal 100%.

This is the logical extension of what you are arguing.

Smee.. so you are saying that an older boy/younger girl is the same as an older girl/younger boy?

Smee.. so you are saying that an older boy/younger girl is the same as an older girl/younger boy?

lol. Are you trying to get him to come out?

Yup, I’m off, smee admitted earlier it was 25:50:25 spread earlier, now he’s denying it.

Trolling

Good fun though!

Funkynick

If you knew neither childs gender

b/b 25%
b/g 25%
g/b 25%
g/g 25%

You know the gender of one so you are left with

g/b 50%
g/g 50%

bless him

Can the mods link this post to all of George’s subsequent posts as a warning either not to take them seriously (as they are trolls) or invalidate the argument being proposed?

I will not change my mind as a result of what others say. You should all know that by now.

Mat – go and do your presentation.

My guess is that he’s either too stupid to realise he’s looking stupid, or he’ll “reveal” that he was trolling all along.

There’s a probability in there somewhere….

Aaaah, so you are admitting you are wrong, but won’t change your mind anyway.

Excellent.

Get got the result chaps!

😀

Not admitting anything. As a person capable of independent thought I’m happy with my arguement.

2 Mat’s (M@’s) on 2 different forums, what’s the probability of it being the same person? :p

Needless to say you’ve upset Tom’s mathsist sensibilities

Pretty good I’d say.

Mathematicians, Engineers, Scientists and Midwives will probably all get different solutions the this puzzle. All will think their solution is correct. Can they all be correct? Yes.

I will not change my mind as a result of what others say. You should all know that by now.

Then. Do. The. Math!

Or try using the spreadsheet as I described above.

Or trying tossing two coins 100 times.
Every time you get two heads then cut you left arm.
Every time you get a head and a tail then cut your right arm.
Once you are finished simply measure the blood loss from each arm. You will find the right one has twice as many cuts as the left and will bleed out quicker.

The Mathematicians, Engineers and Scientists are all agreeing, are you a midwife? 😛

I have done the math. I just think you should all be doing different maths.

Smee… it doesn’t matter what you say, I know that’s what you meant. You lost, and are just too proud to admit it.

I understand probability perfectly well. Many years of doing engineering maths at uni has seen to that.

He is apparently an engineer, but for some reason he uses a different mathematical system from the rest of humanity. I hope you’re not involved in anything critical Smee.

You have been given several clear empirical experiments that produce results which fit perfectly with our answer and you have been unable to find fault in them (and instead you’ve just quietly ignored them).

If your answer (the 50% answer, not the 2:1 answer) is correct then lets hear how we can conduct a simple experiment that backs it up.

Any experiment you like… in your own time…

He is apparently an engineer, but for some reason he uses a different mathematical system from the rest of humanity. I hope you’re not involved in anything critical Smee.

Guess that’s why he became a driving instructor.

well i read my way thru that lot but going back to the original rules – how do we know the lady isn’t a compulsive liar?

Anything yet Smee? Nope thought not. 😀

The coin toss backs it up.

The coin toss experiment that I outlined a few posts ago? That backs up your answer?!?

Or have you devised your own perverted version of it?
Please explain in enough detail that we can try it too.

options for two throws
tt
th
ht
hh

when you know that one is a h you have:
one of ht or th – not both.
and
hh left as possible outcomes after the second throw.

The problem is the over-complicated way the question is being asked. As the gender of one child is already known the remaining and simplest unknown and therefore the only question which needs to be asked is what is the gender of the other child? The answer to this question will answer the original question and has a probability of 50%.

Andy.

Erm.. oh dear.

So you’re saying “It is one of these four possibilities and if you get information that eliminates one of those possibilities then that leaves you with two.”?

one of ht or th – not both

Well actually the result will be one of ht, th or hh – not all three. They are all equally likely though.

No I’m saying that once you know that one is a head then it removes the options that start with a tail.