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Any specific REAL math problems you need help with?


ezex

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Ya of course, this is the tipical IA that's going around. All right, first off you have to realize that what you're trying to do is get a function that fits the data as good as you can. If you haven't already seen statistics, this might be hard to understand, but it really makes no difference as long as you have a graphing calculator (the theory behind it is just a huge formula called linear regression but it only works for lines so don't worry about it)

i understand how you got the function, however, i dont know how to modify the function.

can you show me ways to do it?

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OK tvd7, here goes that last problem:

its fairly simple, just realize that what you have, x-2 + 3iy = 7i, is really just a + bi = c + di, just that a = x-2, b = 3y, c = 0 and d = 7.

so if you have that a has to equal c, then x-2 has to equal zero, meaning that x is 2.

and if b has to equal d, then 3y has to equal 7 meaning that y equals 7/3

done :P

@rongrong: what do you mean?

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I have a question that I'd love to get help with as it has been driving me nuts. I am SL btw :P

It's normal distribution.

X ~ N (20, 12). Find P (X ≤ 16)

I know I should also be able to draw the graph of this but I cannot figure out how either (I have a TI) so if you also know that, it'd be grateful if you could explain how :P

Edited by Afterglow
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I don't usually draw graphs, so I can't help you with that. But for the answer:

Go to Distr, press 2. So that you get normalcdf(

And then, put in, normalcdf(-1000,16,20,12) (assuming that 12 is standard deviation, and not variance, if it's variance then sqrt(12))

To draw it: http://tibasicdev.wikidot.com/shadenorm

http://www.tamut.edu/~dkern/Statistics/Han...ormDistTI83.htm

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I suppose what they can give you is questions about finding the population mean and population standard deviation when you only have 2 probabilities to work on. You can do that using the inverse normal formula: z= mu - omega / n

Are you SL or HL?

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  • 1 month later...

This problem is in a set of differentiation examination question:

A right circular cone of base radius 2 cm and height 6 cm stands on a horizontal table. A cylinder of radius x cm stands inside the cone with its axis coincident with the axis of symmetry of the cone and such that the cylinder touches the curved surface of the cone. The volume of the cylinder is V cm^3.

a. show that V = 6 pi x^2 - 3 pi x^3

b. given that x can vary, obtain the maximum value of V.

Edited by tvd7
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Hey guys, I have a problem with mean/median. Could you please help me to solve the following task?

"The table below shows the marks gained in a test by a group of students.

Mark 1 2 3 4 5

N of st 5 10 p 6 2

The median is 3 and the mode is 2. Find the TWO possible values of p."

Could someone also explain how to do it step by step? Thanks a lot!

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Hey guys, I have a problem with mean/median. Could you please help me to solve the following task?

"The table below shows the marks gained in a test by a group of students.

Mark 1 2 3 4 5

N of st 5 10 p 6 2

The median is 3 and the mode is 2. Find the TWO possible values of p."

Could someone also explain how to do it step by step? Thanks a lot!

all right here goes:

first thing you could do is look at the mode. Now you know that the mode is 2 therefore for mark 3, there can't be more than 9 students (9 or less). Now you look at the median (spread it out so you can see better):

1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3(p times) 4 4 4 4 4 4 5 5.

If you might recall, to find the median you just find the number in the middle. They tell you that the median is three SO you have to think a little here. There are a total of 15 numbers before MARK 3 starts. The median is found by dividing the total number of events by 2 and then finding that number. Therefore, the least number to make the median be 3 is 15 +1 ( +1 because if not it would be 15*2 which would be thirthy and it would give a median of 2.5).

So we have that median = (# of marks + 1) / 2. This will give you the POSITION of the median (if the answer were 18 then you count up to 18 (1 1 1 1..... up to 18 numbers and it should land on a three for it to be correct). So you make the total number of marks be at least 31 so that the median lies in number 16:

1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 (3) 3....

Now don't forget about the value of P. All this tells us is how many total marks we have. So there's fifteen 1s and 2s and eight 4s and 5s for a total of 23 values out of the 31 total. This means there's 8 3's left. This gives the first value of P. Remember that we said that for the mode, there had to be 9 or less people, so p works for 8.

The second value is just making the total number of marks be 32 instead of 31. This will give the following:

Median = (32 + 1) / 2 which gives 16.5. Now think about what this means: 16.5 means the median is between the sixteenth and seventeenth value, but after 15 it's all threes for a while. So between 16 and 17 the value is still 3 which means that for the median, having 32 values works. And this means that there are 9 values of 3 for a final answer of P = 9

So in total, P = 8 or 9.

Call me if you have any other questions :D

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  • 1 year later...

I am confused about question from my Math SL 1 textbook, its in a cumulative review section:

1. A ship travels 300 km south from port and then 120 km on a course of 200 degrees.

a. Make a diagram that illustrates the result of the ship's sailing.

b. Find the ship's current distance and course from port.

-I did part 1a, and drew the diagram. For part 1b, I tried to solve for an angle of the 'triangle' that the ship's course forms, using SinX/x formula, but realized this must not be the the part i am trying to solve for. I know the correct answer should be: 414.8 km, 185.7 degrees. How did they arrive at this answer? Any help would be great! Thank-you!!

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Um, I am not very good at Maths now but I am trying to improve.

I am having a problem on Coordinate Geometry and need help.

By the way, I am revising for my mid-year exam, which is on Monday so

I need a fast reply.--"

It goes like this

Let A and B be the points (0,1) and (2,3) respectively

The point P lieson the line y=2x-9 and is equidistant from A and B. Find the

coordinates of P. The answer for this is (4,-1). A BIG Thank you beforehand.

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Um, I am not very good at Maths now but I am trying to improve.

I am having a problem on Coordinate Geometry and need help.

By the way, I am revising for my mid-year exam, which is on Monday so

I need a fast reply.--"

It goes like this

Let A and B be the points (0,1) and (2,3) respectively

The point P lieson the line y=2x-9 and is equidistant from A and B. Find the

coordinates of P. The answer for this is (4,-1). A BIG Thank you beforehand.

First of all you have that the point P is equidistant from A and B. If we call "d" the distance between two objects we have that:

d(A,P)=d(A,B)

These distances are the magnitude of the vectors AP and BP. Now we have that:

frmula1.jpg

If we operate it, you finally have:

frmula2.jpg

This is the locus of all the possible P points. It's is a line, we can rewrite like:

x+y-3=0

We know that P lies on y=2·x-9. Now we only have to found the intersection:

frmula3.jpg

3x-12=0

x=4

4+y-3=0

y=-1

Ergo, P=(4,-1).

Edited by Toffu-san
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  • 4 weeks later...

Hey. I have a couple of problems :D

The first is a logic problem, and it is in the attached file.

The second is

Find logab given

a = ((tan15)+ (3)1/2 )5

b = 4(cos116cos244 + cos23sin67 + cos67sin23 - sin116sin244)

For the second problem, calculators aren't allowed, but let's say that you know the value of tan15 and sqrt of three because your teacher told you they might show up like this. Also, the angles are in degrees, not radians.

Answer choices: A. pi/2 B. 1/2 C. 3/4 D. 3/5 E. None of the above (or to the side really haha)

Thanks! :D

Logic.docx

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I can't see the first because I'm not VIP, but for the second one you say that you have the value of sqrt (3) and the value of tan(15), you can see that sqrt(3)+tan(15)=2, consequently 2^5=32.

a=32

b: (cos(116)·cos(244) + cos(23)·sin(67) + cos(67)·sin(23) - sin(116)·sin(244))=(cos (116+244)+sin (67+23))

(remember that sin (a+b)=sin (a)·cos(b)+sin(b)·cos (a) and cos (a+b)=cos(a)·cos(b)-sin(a)·sin(b) )

(cos (116+244)+sin (67+23))=(cos (360)+sin (90))=1

b=4·1=4

Now you have this:

log324=2/5

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Haha thanks! I just noticed that tan15 +sqrt3 = 2. :D I never use calculators on this stuff, and the tan15 that I learned involves a complex fraction with square roots. Never knew the decimal equivalent.

One more question.

Rob, Robby, and Roberta play a game with a fair, single six-sided die. Rob rolls first and wins if he rolls a 1. If he does not roll a 1, Robby rolls. He wins if he wins a 1 or 2. If he doesn't win, then Roberta rolls. Roberta wins if she tolls a 1, 2, or 3. If Roberta does not win, then the game starts over. What is the absolute value of the difference between Robby and Roberta's changes of winning?

A. 0 B. 1/9 C. 1/36 D. NOTA

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