If you guess "Prime" or "not Prime" with a 50-50 chance, then whichever one is right, you have a 50% chance of choosing that one. So, yes, you did it right.

With a 50% chance, 7 out of 12 isn't very significant. 8/12, maybe, but not 7/12.

## Search found 206 matches

- Tue Nov 17, 2009 12:15 am UTC
- Forum: Mathematics
- Topic: Quick Probability Question
- Replies:
**5** - Views:
**902**

- Fri Nov 06, 2009 1:08 am UTC
- Forum: Gaming
- Topic: Favorite game of all time?
- Replies:
**79** - Views:
**8463**

### Re: Favorite game of all time?

La-Mulana- for its music, atmosphere, difficulty, and most of all charm.

A close second would be Touhou: Imperishable Night, for most of the same reasons.

A close second would be Touhou: Imperishable Night, for most of the same reasons.

- Fri Oct 30, 2009 6:05 pm UTC
- Forum: Mathematics
- Topic: Apparently easy complex number problem
- Replies:
**20** - Views:
**2100**

### Re: Apparently easy complex number problem

Think about it geometrically. If z/(z-i) is real, z and z-i have the same angle from the origin (because division of complex numbers subtracts the angles.) So, 0, z, and z-i are all in a straight line. But z-i is directly vertical from z, so z must be directly vertical from 0. Theref...

- Wed Oct 28, 2009 9:22 pm UTC
- Forum: Coding
- Topic: Project Euler
- Replies:
**411** - Views:
**157093**

### Re: Project Euler

Oh, silly me. It works now, thanks!

- Tue Oct 27, 2009 11:54 pm UTC
- Forum: Coding
- Topic: Project Euler
- Replies:
**411** - Views:
**157093**

### Re: Project Euler

I'm doing #14: n -> n/2 if n is even n -> 3n+1 if n is odd Which number under 1,000,000 takes the longest to get to 1? My algorithm is a sort of "branching out" thing. I start with 1, and in each step: 1) If n was just added to the list, add 2n to the list. 2) If n was just added to the li...

- Tue Oct 27, 2009 11:36 pm UTC
- Forum: Mathematics
- Topic: optimization - help needed
- Replies:
**8** - Views:
**1010**

### Re: optimization - help needed

Oblivion wrote:SA=2x^2+4xy+2x+4y = 162.24

Oblivion wrote:solving for y, 2x^2+2x-162.24=4xy+4y

Oblivion wrote:(2x^2+2x-162.24)/4y=x

Maybe I'm just being silly, but I think you made an error here.

EDIT: Also, a hint: don't try to get x=(something), try to get y=(something). It works out much nicer.