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## #10101 2013-04-15 02:13:33

anonimnystefy
Real Member

Offline

### Re: Linear Interpolation FP1 Formula

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

## #10102 2013-04-15 02:17:08

bobbym

Online

### Re: Linear Interpolation FP1 Formula

I thought I did. The book stiffens up after the first two chapters. I can only get small pieces of it. There is some stuff in later chapters.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10103 2013-04-15 08:27:23

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

And the 3-day streak is broken -- nothing from adriana today. Perhaps she is just busy.

## #10104 2013-04-15 08:35:52

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Or she could be out there finding doctors who want to take blood from her.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

zetafunc.
Guest

I hope not...

## #10106 2013-04-15 08:39:15

anonimnystefy
Real Member

Offline

### Re: Linear Interpolation FP1 Formula

#### bobbym wrote:

I thought I did. The book stiffens up after the first two chapters. I can only get small pieces of it. There is some stuff in later chapters.

Hm, the third chapter will really bee a tough nut to crack.

Hi zf.

You guys managed to go over 10000 posts in a thread! That is more than most members on the forum have.

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

## #10107 2013-04-15 08:41:58

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Yes an amazing accomplishment.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10108 2013-04-15 09:33:52

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

10,000 posts... H would be proud.

## #10109 2013-04-15 09:34:58

bobbym

Online

### Re: Linear Interpolation FP1 Formula

It would give her something to aspire to.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

zetafunc.
Guest

## #10111 2013-04-15 09:50:30

bobbym

Online

### Re: Linear Interpolation FP1 Formula

I would not worry about it. They love attention, good or bad really doesn't matter.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10112 2013-04-15 19:45:30

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

Who knows what she is doing now...

I am stuck on a probability problem -- from STEP III 1999 Q13 (unfortunately there aren't official solutions for this problem, only an unofficial one which I can't follow):

"The cakes in our canteen each contain exactly four currants, each currant being randomly
placed in the cake. I take a proportion X of a cake where X is a random variable with density
function

f(x) = Ax

for 0 ≤ x ≤ 1, where A is a constant.

(i) What is the expected number of currants in my portion?
(ii) If I find all four currants in my portion, what is the probability that I took more than
half the cake?"

First part seems pretty straightforward.

So f(x) = 2x.

The 4 currents are randomly distributed, so the expected number of currents in my portion is 4*(2/3) = 8/3.

I can find the probability of taking more than half the cake (integrating the PDF between 1/2 and 1 gives 3/4), but not sure what to do about the 4 currants in my portion. It's a conditional probability so I'd also need to know how to find the probability of having 4 currants AND more than half the portion, and I don't know how to do that...

## #10113 2013-04-15 20:38:39

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Hi;

First part looks okay.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10114 2013-04-15 20:39:55

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

Thanks -- what can I do about the second part?

## #10115 2013-04-15 20:46:28

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Hi;

That is what I am working on right now but not doing so well.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10116 2013-04-15 20:53:30

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

That's how I feel about most questions in STEP III...

## #10117 2013-04-15 21:01:56

bobbym

Online

### Re: Linear Interpolation FP1 Formula

That is how I feel about math in general, I am checking some texts for a similar problem because I do not have one solved in my notes.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10118 2013-04-15 21:58:56

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Hi;

Sorry to take so long. I have this guys answer
http://www.thestudentroom.co.uk/showthr … st18366432

It seems to correspond to a simulation I ran. I just do not understand his first step!

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10119 2013-04-15 22:22:37

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

Thanks -- that's the one I've been struggling to understand too. I don't understand the x^4 thing...

Unfortunately it is the only solution I can find on the internet.

## #10120 2013-04-15 22:28:40

bobbym

Online

### Re: Linear Interpolation FP1 Formula

They say that solution is correct later on but I do not get the X^4 either.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10121 2013-04-15 22:40:12

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

He has said P(4 currants in a portion) = E(X^4)... not sure what to make of that.

Does that imply P(1 currant in a portion) = E(X)?

## #10122 2013-04-15 22:53:13

bobbym

Online

### Re: Linear Interpolation FP1 Formula

Hi;

I do not know the answer to that one. I can not see why he can multiply like that or whether that relation you are stating holds.

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10123 2013-04-15 23:05:41

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

He is multiplying because

I'm still not getting that g(X) = X^4 though...

## #10124 2013-04-15 23:11:15

bobbym

Online

### Re: Linear Interpolation FP1 Formula

This is what I meant:

Now taking a proportion X of the cake gives probability X^4 that all 4 currents will be in that portion.

Does that integral you posted apply here?

In mathematics, you don't understand things. You just get used to them.
Some cause happiness wherever they go; others, whenever they go.
If you can not overcome with talent...overcome with effort.

## #10125 2013-04-15 23:31:13

zetafunc.
Guest

### Re: Linear Interpolation FP1 Formula

I still can't understand why he did that. Everybody afterwards just says they agree with it, even though the original poster says he's not certain it's correct.

Then again I can't think of what other options there are...