Pages: 1 [2] 3 4   Go Down
Author Topic: Faites vos jeux messieurs, dames  (Read 2718 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

PART 1 - I have two children. One of them is a boy. What are the odds that the other is also a boy?
@robtillaart correctly answered 1:3 or 33% (he also jumped the gun a bit on the next part)

So now onto the interesting bit;
PART 2 - I have two children. One of them, the thinnest, is a boy. What are the odds that the other is also a boy?

Cards on the table folks.
Logged

Leighton Buzzard, UK
Offline Offline
Edison Member
*
Karma: 21
Posts: 1339
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You probably want to say same as case 1
Logged

there are only 10 types of people
them that understands binary
and them that doesn't

Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
You probably want to say same as case 1
No I want you to tell me if the fact that this time the boy is thin changes the odds or not.
Place your bet.
Logged

Leighton Buzzard, UK
Offline Offline
Edison Member
*
Karma: 21
Posts: 1339
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Odds unchanged
Logged

there are only 10 types of people
them that understands binary
and them that doesn't

Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Messieurs, dames - the first bet has been placed that skinny children don't change the odds.
Get your money on the table.



Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 474
Posts: 18696
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Are we talking probability here or DNA? You mentioned DNA in the first post.
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 474
Posts: 18696
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

So now onto the interesting bit;
PART 2 - I have two children. One of them, the thinnest, is a boy. What are the odds that the other is also a boy?

Based on reading this: http://en.wikipedia.org/wiki/Boy_or_Girl_paradox

I would say 1:2 chance.
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 474
Posts: 18696
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

My justification is along the lines of reply #10.

Assume we have four possibilities:

Code:
TB G
TG B
TB B
TG G

Where T stands for thinnest.

Given that we know that we have TB (thinnest/boy) then we are left with:

Code:
TB G
TB B

Only two left, so there is a 50% possibility of a girl.
Logged

Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
Are we talking probability here or DNA? You mentioned DNA in the first post.
Nothing to do with DNA just probability.

This truth table is incorrect for several reasons by the way
Code:
TB G
TG B
TB B
TG G
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 474
Posts: 18696
Lua rocks!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Your claim is incorrect however the proof is too large to fit in the margin.  smiley-razz
Logged

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13477
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
Nothing to do with DNA just probability.
Always understood that the way DNA combines (to create a new creature great or small) has a lot to do with probability.
I recall studying Mendel's probability law's with drosophila melanogaster (fruit fly) during biology.
Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

We have two bidders one that the skinny boy does not change the odds at 1:3 or 33% and the other that the boy being skinny does change the odds to 1:2 or 50%.

Any one else going to take a side?
Logged

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13477
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I'm with Nick (#22) => 50%
« Last Edit: August 25, 2013, 07:07:00 am by robtillaart » Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Offline Offline
God Member
*****
Karma: 7
Posts: 647
"In this house, we obey the Laws of Thermodynamics" Homer J. Simpson
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Nick and Rob have the right answer 1:2 50% though Nick's reasoning was not quite correct - will post post full answer later.

Is it not bizarre though;
If I tell you I have two children one of whom is a boy the odds of me having two boys is 1:3 33%, yet if I tell you I have two children one of whom is a boy who happens to also be my thinnest child the odds of me having two boys is 1:2 or 50%.

No tricks, no genetics, just maths!
Logged

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 211
Posts: 13477
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Another riddle: (this one took me some time)

A man has three children.
The product of their ages is 36.
The sum of their ages is the number of cars in my street.
And to determine their ages you must know that the youngest was ill recently.
How old are the kids?

(yes you need al the information)

Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Pages: 1 [2] 3 4   Go Up
Jump to: