1. 100% cuz they already have or 1%/90% varying % depending on wheter you use condom or not next time

---------- Post added 2010-12-21 at 01:03 PM ----------

Originally Posted by Ajtbagger
make it understandable.

im not 100% sure what you mean.

assuming both children are boys 0% cause they already are brothers.
if a riddle is understandable,where is the riddle?

2. 50%. If you have a son, then the other is 50/50 chance of being a boy, and therefore a brother.

3. We know:
I have two children
one of them is my son(boy)

how big is the chance that my son has a brother? not that hard right? |_|

like 1/8 (no thats not the solution)

4. Can't know.
there may be diffrent mothers, therefore they're not ''fully'' brothers.

5. Originally Posted by Chippr
Can't know.
there may be diffrent mothers, therefore they're not ''fully'' brothers.
it's the same mother =)

6. Originally Posted by Grinder
I have two children

How big is my sons chance to have a brother?

make a guess!
There are 4 possible gender combinations of 2 siblings:
BG, BB, GB and GG

Since we only know 1 is a son, but not whether the first or second sibling is a son we're left with 3 possible combinations:
BG, BB and GB.

Subtract 3B's and we're left with GGB. I'd say 1/3rd chance of your son having a brother.

7. He has a sister so 0% chance?

8. Originally Posted by Grinder
We know:
I have two children
one of them is my son(boy)

how big is the chance that my son has a brother? not that hard right? |_|

like 1/8 (no thats not the solution)
the other might or might not be a brother of his, it might also be a girl.

so I'd say 25%

9. Originally Posted by Huibert-Jan
There are 4 possible gender combinations of 2 siblings:
BG, BB, GB and GG

Since we only know 1 is a son, but not whether the first or second sibling is a son we're left with 3 possible combinations:
BG, BB and GB.

Subtract 3B's and we're left with GGB. I'd say 1/3rd chance of your son having a brother.
You solved the riddle!

It's as he says, its a 1/3 chance

wanna go for another one? yay

10. That's really not a riddle unless i'm misunderstanding it.
It depends as you said sons which could lead us to mean it's plural and your referring to both children (100%), or it could mean possessive and your just referring to one child in which case the answer is either 0% or 100% depending on the sex of the other child which we have no way of knowing.

11. Here's a lil one for the new ones

Peters Mother has three children: Tick Trick and... ?

make a guess

12. Peter.

The mother has Peter, Tick and Trick as her sons.

13. Originally Posted by Huibert-Jan
There are 4 possible gender combinations of 2 siblings:
BG, BB, GB and GG

Since we only know 1 is a son, but not whether the first or second sibling is a son we're left with 3 possible combinations:
BG, BB and GB.

Subtract 3B's and we're left with GGB. I'd say 1/3rd chance of your son having a brother.
Thats totally wrong. You have to pay attention to which sibling you are talking about, you can't just switch them around in the combination. BG is not the same as GB because its a different kid. If we know the first child is a boy then GB isn't a possible combination and is ruled out.

Given our combinations of BG, BB, GB, and GG if we know one slot is a B then we eliminate all combinations where that isn't the case; if its the first slot then BG and BB remain. If its the second, BB and GB remain. GG isn't a possibility, and one of the B+G combinations is eliminated.

The thing is, we can't know the probability of the second child being a boy or a girl from that alone. Just because we have assessed that there are two options doesn't mean that they are equally likely. Simply due to population trends, it is slightly more likely that the other child is a girl. Not much though, something like 52% preference.

14. Originally Posted by Grinder
You solved the riddle!

It's as he says, its a 1/3 chance
This is false. Take for instance, flipping a quarter. You can have HT, TT, HH, TH. However, the outcome of the second flip has NOTHING to do with the outcome of the first flip. Both are 50/50 (ignoring genetic pre-disposition towards a gender).

15. No, thats wrong Grinder. You stink at probability.

16. Peters Mother has three children: Tick Trick and... ?

Peter

17. Originally Posted by Phage0070
No, thats wrong Grinder. You stink at probability.
Then tell me your math, ill tell you mine if you want but i dont want to hurt your ego =)

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