Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## #1 2011-02-14 00:38:11

gAr
Star Member

Offline

### Probability, 2 fair coins

Hi all,

2 fair coins are flipped and atleast one of the outcomes is known to be a head., what is the probability that both outcomes are head?

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #2 2011-02-14 00:45:53

bobbym

Offline

### Re: Probability, 2 fair coins

Hi;

Looks good to me!

http://trickofmind.com/?p=439

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2011-02-14 01:00:51

gAr
Star Member

Offline

### Re: Probability, 2 fair coins

Hi bobbym,

Thanks for looking into it, and thanks for the link!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #4 2011-02-14 01:11:10

bobbym

Offline

### Re: Probability, 2 fair coins

Hi;

Just be careful some of those guys at that link are wrong.

http://www.cse.buffalo.edu/~atri/course … lect4.pdf.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #5 2011-02-14 01:25:03

gAr
Star Member

Offline

### Re: Probability, 2 fair coins

Hi,

yes, I verify before accepting any answer!

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."

## #6 2011-02-14 22:54:46

Howardroark
Power Member

Offline

### Re: Probability, 2 fair coins

Hi gAr,

#### gAr wrote:

2 fair coins are flipped and atleast one of the outcomes is known to be a head., what is the probability that both outcomes are head?

You are right.. Here's a problem similar to yours..

A couple has 2 children. One of them is a girl. What is the probability that the other is a girl?

I come from a civilization which has given the world the number 0..

## #7 2011-02-15 01:59:10

gAr
Star Member

Offline

### Re: Probability, 2 fair coins

Hi Howardroark,

Thanks for looking into the problem.

"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."