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+118725

bump

MelodyFeb 3, 2014

#67

+118725

bump

MelodyFeb 3, 2014

+118725

asdt:
:| what is all the numbers of pie

Pi is an irrational number.
This means that it cannot be written exactly as a fraction or as a terminating decimal. It can't even be written as a recurring decimal.
no matter how many digits you find, there will ALWAYS be more to be found.

Here is just a few of the digits of pi

pi.JPG

MelodyFeb 3, 2014

+118725

mohamedabdelatey:
how can i make cos inverse

huh?
press shift cos

Inverse cos is what you use if you have got the cos answer but you want to find the angle

inverse cos is the same as arccos

MelodyFeb 3, 2014

+118725

slothz:
A machine purchased for $400 000 depreciates at a rate of 20% p.a. After how many years
will the machine have a value of $131 072?
Just don't really know the formula for calculating n plz help
Cheers guys

hI,
what nice manners , thank you.

It is almost the same formula as compound interest which is S=P(1+r) ⁿ
Where S is the future value,
p is the present (or initial) value,
r is the interest rate per compounding period
n is the number of compounding periods

The only difference is that if interest is compounding the amount is getting bigger so it is (1+r)
If the item is depreciating the amount is getting smaller so you use (1-r)

A machine purchased for $400 000 depreciates at a rate of 20% p.a. After how many years will the machine have a value of $131 072?
So the formula you need to use is S=P(1 -r) ⁿ
S is the future value = $131 072
P is the initial value = $400 000
r = 0.2
n = unknown

131 072 = 400 000(1-0.2) ⁿ
divide both sides by 400 000
0.32768 = (0.8) ⁿ

Now, whenever the exponent is the unknown, you have to use logs to solve the question
It doesn't matter what base you use, the calculator deals only with 10 and e so you'd best choose one of those.

log 0.32768 = log (0.8) ⁿ

log 0.32768 = n * log 0.8

n = log 0.32768 / log 0.8
and you can finish it.

Here are the log identities, there are a lot that you are expected to remember.
http://en.wikipedia.org/wiki/List_of_logarithmic_identities

MelodyFeb 3, 2014

+118725

Guest:
4.46 x 10^-6, Move the decimal 6 places to the left.

0.- - - 446
Fill in the spaces with zeros
Answer: 0.000446

Good try but not quite,
there are not enough zeros

4.46 x 10 ^-6

= 0.00000446

The 46 were already after the point.
you had to jump over the first digit '4' and then five zeros until you got were you needed to go. I put the 0 out the front just to make it easier to read.

Would you like to try another one?

how about
8.903 x 10 ⁵

MelodyFeb 3, 2014

+118725

Guest:
4.46 x 10^-6, Move the decimal 6 places to the left.

0.- - - 446
Fill in the spaces with zeros
Answer: 0.000446

Good try but not quite,
there are not enough zeros

4.46 x 10 ^-6

= 0.00000446

The 46 were already after the point.
you had to jump over the first 4 and then five zeros until you got were you needed to go. I put the 0 out the front just to make it easier to read.

Would you like to try another one?

how about
8.903 x 10 ⁵

MelodyFeb 3, 2014

+118725

Guest:
(5^2+2x-1)+(-4^2+x+7)

(10+2X-1)+(-8+X+7)

(2X+9)+(X-1)

Answer: 3X+8

Hi Guest, thank you for contributing to this question. It is good when people join in.
most of you answer is correct.
However,
In this question the hat ^ is used to indicate power or exponent. So 5^2 means 5 ² which is 5*5 = 25
Often on the forum you will see a multiply sign written as a * This is so that it won't get confused with a x if the question has algebra in it.

So the question really is and since there is a plus in between the brackets i can just leave it out

= 5^2+2x-1+ -4^2+x+7
= 5*5 + 2x - 1 + -4 ² + x + 7

Now, -4^2 is really tricky. Is it -4*-4 = +16? or is it - 4*4=-16 It is always best to use brackets in a situation like this so that the message is clear.
If you do it on your calculator with no brackets you will get -16 Try it and see.
The reason is that the calculator interprets it like this -4^2 = -4 ²= -1 * 4 ²

To be perfectly honest I am not sure how a person is supposed to interpret this. I will ask the other mathematicians whether they have a definite take on this.

For the moment I will interpret it like (-4) ²= -4*-4 = +16 Because I think that was the intent but this does need to be checked.
so

= 5*5 + 2x - 1 + (-4 ) ² + x + 7

= 25 + 2x -1 + +16 + x +7

= 25 -1 + 16 + 7 + 2x + x

= 25 -1 + 16 + 7 + 2x + x

= 47 + 3x

= 3x + 47 (It is always nice to put the x term before the constant)

MelodyFeb 3, 2014

+118725

Guest:
SIMPLIFY 9X+3Y

Hi Guest thank you for your contribution to this problem. I am sure that you were not the only one confused by my answer.

Hi guest, if you are asked to factorise 9X+3Y then the answer is indeed 3(3X-Y) So you can think of factorise as meaning 'put brackets in' if you like.

The factors are 3 and 3X-Y because when you multiply them together you get 9X+3Y

HOWEVER

The question says simplify. simplify means take away the brackets, not put them in!

Therefore 9X+3Y is already as SIMPLE as it can be.

MelodyFeb 3, 2014

+330

Shoni wrote: This is my first time using a web calculator. Can someone please provide me with instructions on how to calculate the Pearson's r and coefficient of determination using a web calculator.
Thank you

************
For clarification: Pearson's r, is the coefficient and it's value determines the nature of the data (described below).

The web2.0calc.com calculator has many advanced functions, but statistics is not one of them. Basically, just Permutation and Commutation (called "Binomial coefficient" for this calculator) are the only two directly input able functions for statisticals -- This calculator does not have a Sigma (summation) function or any regressions functions.

While performing statistical calculations on a calculator is possible, it is a very labor intensive and error-prone process. It's analogous to filling a swimming pool with an teaspoon. (A calculator is better than a slide-rule, however). Statistical calculations are best served via a computer more than a calculator.

If you want a very advanced statistical analysis program, "Statistical -R" (the latest version 3.0.2 is available here: www.r-project.org) is a free software programming language for statistical computing and graphics. The program is developed by and for statisticians,mathematicians. It is truly amazing!

Pearson's r, coefficient is basically a least squares slope intercept through data points (X _i,Y _i). The resolved value is from -1 to +1 and indicates correlation of X to Y. The current recommended use for the Pearson product-moment correlation coefficient, the original name of the 130 years-old formula, is on data that is only distributed normally, with minimum of 30 data pairs, and with less than 5% of the data more than one Standard deviation out, and no data points more than 2SDVs out. It is a simple process and there are two methods use to calculate it's value.

For an online calculation, the site listed below should suffice. I don't know how many data pairs you can enter, but it should be at least 30, else the results are unreliable.

www.socscistatistics.com/tests/pearson/Default2.aspx

This ends the editorial and commentary -- I hope it helps.

~~D~~

DavidQDFeb 3, 2014

+6252

to do them? what do you mean?

to get the integers take all the positive numbers 1, 2, 3 .....
now take the negative of each one of those -1, -2, -3....
now add 0.
All of those numbers together make up the integers.

take any two integers a and b, where b isn't 0. a/b is then a rational number

To get the irrational numbers take all of the real numbers.
Now toss out the rational numbers. What's left is the irrational numbers.

RomFeb 3, 2014

+6252

add 12 to both sides

RomFeb 3, 2014

1.60934 km= 1 mile

3.02 km/1.60934 km = 1.87 miles

GuestFeb 3, 2014

4.46 x 10^-6, Move the decimal 6 places to the left.

0.- - - 446
Fill in the spaces with zeros
Answer: 0.000446

GuestFeb 3, 2014

(5^2+2x-1)+(-4^2+x+7)

(10+2X-1)+(-8+X+7)

(2X+9)+(X-1)

Answer: 3X+8

GuestFeb 3, 2014

3(3X+Y)

GuestFeb 3, 2014

The square root of 1 is 1 because 1*1 is 1.

GuestFeb 3, 2014

+118725

Guest:
SIMPLIFY 9X+3Y

This cannot be simplified,

MelodyFeb 3, 2014

+118725

Guest:
5. Plot the complex number .-4sqrt(3) -4i

I think that you just plot (-4sqrt(3),-4)

but the x axis is actually the Real axis
and the y axis is the i axis.

MelodyFeb 3, 2014

+118725

kseniya:
what is the equation of a line that passes through the points (-4,-5) with the slope of -7/2

Hi kseniya,

Use the forumula

y-y ₁=m(x-x ₁)

Can you do it now?
Have a go, if you get in a mess post again but show me what you have tried already.

MelodyFeb 3, 2014

+118725

latreace:
billy, sam, and cat is having a candy party there are 13 pieces of candy. how many pieces of candy can billy, sam, and cat have?

well billy gets 1 piece
Sam gets 1 piece
and it is Cat's birthday so she gets 11 pieces.

MelodyFeb 3, 2014

+118725

drewace22:
a minute hand on a clock is 80 cm long. how far does the tip of the minute hand travel in 30 mins?

It will travel half of the circumference.

so that's 1/2 * (2 * pi * r)

What is r? Draw the picture and you will see.

You can finish it.

MelodyFeb 3, 2014

+118725

janeenaj25:
55+7x+4x=180 what is x ?

well +7x+4x = +11x ( the sign always belongs to the thing behind them, with plus this is easy, with minus you have to be careful.)
55 is really +55

so we have
+55+11x = 180

Now, you want the lots of x on their own. So you need to get rid of the +55 , you will have to take 55 off both sides

55+11x-55 = 180-55

11x = 125
Now to get the x by itself, you have to divide both sides by 11
You can finish it

MelodyFeb 3, 2014

+118725

emili.spruills21:
x^2-4x+1

This is not a question.
If you intended it to be equal to zero then use the quadratic equation.
Here it is. Copy an paste it into your browser.

http://www.youtube.com/watch?v=O8ezDEk3qCg

MelodyFeb 3, 2014

+118725

yamile:
how to calculated binomial distribution

this is a video that might help.

http://www.youtube.com/watch?v=1pSD8cYyqUo

MelodyFeb 3, 2014

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