Mathematics - 4 September 2006

I hate just asking the same questions from the assignment, but time's running out and I've never done anything like this before, so I know if I try to work through it and ask specific questions I'll get nowhere, but if I ask hopefully someone can explain. So:

The random variable X measures the concentration of ethanol in a chemical solution, and the random variable Y measures the acidity. They have a joint probability density function f(x,y) = A(20 – x – 2y) for 0<=x<=5 and 0<=y<=5 and f(x,y)=0 elsewhere.
A)What is the value of A?
B)What is P(1<=X<=2, 2<=Y<=3)?
C)Construct the marginal probability density functions fX(x) and fY(y)
D)Are the ethanol concentration and the acidity independent?
E)What are the expectation and the variance of the ethanal concentration?
F)What are the expectation and variance of the acidity?
G)If the ethanol concentration is 3, what is the conditional probability density function of the acidity?

Explanations, not just answers, please.

2006-09-04 17:33:05 · 1 answers · asked by Anonymous 3

An airplane is flying at a speed of 340 mi/h at an altitude of one mile and passes directly over a radar station at time t = 0.

There are 3 parts to this question. I found the first part but need the second two.

(a) Express the horizontal distance d (in miles) that the plane has flown as a function of t.
d(t) = 340t

(b) Express the distance s between the plane and the radar station as a function of d.
s(d) = ???

(c) Use composition to express s as a function of t.
s(t) = ???

2006-09-04 17:13:00 · 3 answers · asked by Anonymous

Find a formula for the function. Express the surface area S of a cube as a function of its volume V. S(V) =

2006-09-04 17:07:48 · 8 answers · asked by Anonymous

The weight of a certain type of brick has an expectation of 1.12kg with a standard deviation of .03kg.

Find: expectation and variance given 25 randomly selected bricks, and number of bricks necessary to have a standard deviation of .005 or less.

I know expectation is 1.12kg, and I know two formulas for variance, but neither of those are applicable here. What's the formula to use?

And for the other part of the question, I understand why there's a certain number, but short of trial and error I can't think of a way to actually calculate it. Tips?

2006-09-04 16:51:45 · 1 answers · asked by Anonymous 3

2006-09-04 16:44:25 · 5 answers · asked by bobthefrog1114 2

I'm in university doing a B.A. in Pure Math, one year away from graduation. I've got a 4.0 gpa, near the top of my class, doing honours and all that, blah blah blah blah. The thing is: I'm not interested in doing math as a career, but I feel kind of trapped by my degree. My profs are no good for advice, because they all just went straight to grad school, and then went straight into teaching.

I mean, math is a great thing to study, but I'm not a diehard, and I don't want to be.

Any of you math grads have advice for me?

2006-09-04 16:07:54 · 9 answers · asked by Anonymous

would you solve x^2=x to end up with the answer x=1 and x=0?

It's the example to a problem I'm working out....

2006-09-04 16:07:34 · 8 answers · asked by egyptsprincess07 3

and i already know there are waaay more than 64

2006-09-04 15:59:28 · 21 answers · asked by Anonymous

Find the exact length of the interval [a,b] for ln^2(x)-2ln(x)-4=0.

I need to know what to do PLEASE!!

2006-09-04 15:37:46 · 6 answers · asked by Th_hT 1

2006-09-04 15:37:16 · 24 answers · asked by duyanh_mvp06 1

For the people that are good at math please help me! THANK YOU!!

2006-09-04 15:18:27 · 8 answers · asked by sweetxbobah 1

^ is the power of

Decide whether the function is linear. Then evaluate the function for the given value of X.

2006-09-04 15:11:07 · 8 answers · asked by zachvh3 2

2006-09-04 15:02:05 · 5 answers · asked by Anonymous

if a fair coin is tossed 8 times and heads comes up all 8 times, what is the probability that tails will cime up on the 9th toss??

2006-09-04 15:01:20 · 10 answers · asked by Lori 1

Decide Whether the function is linear. Then evaluate the function for the given value of X.


f(x)=2; F(-4)

2006-09-04 15:01:19 · 13 answers · asked by zachvh3 2

B. How do you find in which quadrant an ordered pair is located?
C. How do you use a graph to build a table?

2006-09-04 14:55:24 · 4 answers · asked by thelmadc06 1

given the following numbers, find their greatest common factor(GFC).
16 20

2006-09-04 14:53:15 · 14 answers · asked by Lori 1

2 anglesof a triangle measure 74 degresss and 41 degress find the measure of the missing angle. How would you classify this triangle?

2006-09-04 14:51:41 · 9 answers · asked by Lori 1

what cordinates(+ - x & divide)

2006-09-04 14:41:53 · 6 answers · asked by brown-eyed cutie 2

I can't seem to do LOG. How do I enter, for example,


LOG3 729?

3 is a subscript


answer SHOULD be 6

2006-09-04 14:36:35 · 5 answers · asked by doodooman 1

Ok Tell Me how you got the answer if you get it:

Note: Ignore The ` Because That Has nothing to do with the problem

What does N equal?

48% = 12
``````````—
```````````n


n% = 3
```````—
````````5

2006-09-04 14:35:29 · 5 answers · asked by Veronica ♥ 5

plz explain as well

2006-09-04 14:05:49 · 17 answers · asked by Anonymous

i tried many times to solve this but i cant seem to do it...help?
correct answer: 49.5

A man drove to the beach at an average speed of 55 mi/h and returned home over the same route at the average speed of 45 mi/h. It took him 2 hours longer on the return trip. What was his average speed?

2006-09-04 14:01:09 · 4 answers · asked by ☆----|| 。。¤ ¥ ąйGel ♥ ♀♂。。||---- 2

Pattern:

1, 1/4, 1/9, 1/16

How is this pattern so?

My teacher just gives us random pages, so I have no clue because the book doesn't explain well. Honestly, can you help please?

Please explain symbols too... :o)

2006-09-04 14:00:32 · 5 answers · asked by mani boo/poo 2

From what I understand, a radian is a form of angle measure where it has 1 radian if the length of the radius is equal to the length of arc. But here's what confuses me, there are approx. 6.28 radians in a circle, but what if there is an arc created by a 170 degree angle. then there can be no more than 2 radians? Dammit I dont know my trig book really sucks. Someone please EXPLAIN to me radians clearly. Also what does subtend mean? I asked that earlier but I got 6 different anwers? Does it mean limited or connected to or what?

2006-09-04 13:49:58 · 13 answers · asked by jacksonxxxrrr 1

For clarification to get the idea of my problem....
ex. sqrt4 is 2
^2sqrt4 is also 2
^3sqrt8 is also 2

2006-09-04 13:45:08 · 2 answers · asked by cheezzznitz 5

: )

2006-09-04 13:37:49 · 31 answers · asked by Ginnykitty 7

2006-09-04 13:33:46 · 9 answers · asked by h.lynngee@sbcglobal.net 2

ok this is more of an abstract thought but since it's about numbers it belongs in the mathematics section. odd numbers are symettrical in that they have a naturally equal center point (lets call it piggy in the middle theory) whereas even numbers have to split a central number in two to be even. it's just one of those things that has always bugged me anybody got any far out thoughts on it?

2006-09-04 13:33:15 · 24 answers · asked by Wiseguy 3

2006-09-04 13:21:56 · 21 answers · asked by WINNER 1