All Answers

+118725

mahdy:
:D known coordinates of the point k (1,6), L (-2.1)M (1, -4). if add a point N to KLMN rhombic, then coordinate point N is

Hi mahdy,
Have you tried plotting these points on some graph paper? The answer will most likely jump out at you. Remember, a rhombus is a pushed over square.

MelodyMar 19, 2014

+118725

Shermanator02:
round 7,450,774,796 to the nearest billion?

Australian billion is different from the US billion.
Australian billion is 1 million million = 1,000,000,000,000
US billion is 1 thousand million = 1,000,000,000 (It is much smaller- 1000 times smaller)

Australian 0
USA 7billion or 7,000,000,000

MelodyMar 19, 2014

#75

+118725

Good evening all,
I think that may be the first day where we had more than 1 page of questions!
Great answers from Alan, Samgelinas, highschooler, Rom, CPhill, hihihi, Snipesgaming, guest, and Kitty<3. Thank you.
There were a couple of others as well but since they came without working, they were not of much value.
There were also a couple of nice thank yous given from Zack7713 and a guest. We always like it when people show their appreciation.

I purposely did not answer many questions (I tried not to answer any) on the first round. I think it is more important for me to:
a) check that all proper questions receive answers.
b) check as many of the submitted answers as possible and to input only when I want to add something. I hope no one gets offended by this.

Today, I was busier than I really wanted to be. There are a couple of answers from Chris that I really want to learn from but it will have to wait for a less busy time.

There was a probability question that Chris (CPhill) and I both answered and we did get the same answer. However, neither of us is very confident with our probability ability and I would like someone who is confident to check the answer please. This is the address. http://web2.0calc.com/questions/probability_18

I think that is finally it for this Tuesday/Wednesday.
Melody.

MelodyMar 19, 2014

+118725

julietjj:
Divide (4x^5+3x^3-2x^2) by 2x.

I just did a stack of work for this question before I realised how simple it is.

You can factorise the 2x straight out of the bracket. then you can just cancel the 2x, top and bottom and there is your answer.

(4x^5+3x^3-2x^2) / (2x)

=2x(2x ⁴+(3/2)x ²-x) / (2x)

= 2x ⁴+(3/2)x ²-x

MelodyMar 19, 2014

+118725

joshuanowland:
What is the displacement of a travelling 20km South, then 9km west, then 11km South, then 3km West. Round the answers to two decimal places.

Answers in km and degrees

Hi Joshua,
Kitty had the right idea, here is the rest of the answer.

140319 displacement..JPG

MelodyMar 19, 2014

+130561

Let "x" be the amount the bottle can hold.

Then, the difference between being (1/4) full and (2/3) full = 500ml.

In math terms, we can write (2/3)x - (1/4)x = 500

Or , put anther way, (2/3 - 1/4)x = 500

So we have (5/12)x = 500

Multiply by (12/5) on both sides

So, we have x = 500*(12/5) = 1200ml

Check to see that this makes sense!! 2/3 of 1200 = 800 1/4 of 1200 = 300 800 - 300 = 500

And there you go......

CPhillMar 19, 2014

+118725

kitty<3:
Hello cheetah970,

Yes, there is. I haven't tried this, but the administrator posted it a long time ago. Here is the link:
http://web2.0calc.com/questions/systems-of-equations

For the equations:
2y-3z = 4
-y + 7z = -12

You would put in something like this:
solve( 2 * y - 3 * z = 4 , - y + 7 * z = - 12)

But I tried your equation, and strangely it doesn't work. Maybe it is a typo?
Sorry I couldn't help a lot; maybe when Melody or some of the other people come on they may be able to help you:)

I am just playing with what Kitty has shown me, I haven't played with this before.
The first 2 equations give errors, the next 2 give wrong answers the last one, that admin did, gives an answer. I haven't checked the answer but I assume it is correct. Maybe I shouldn't assume that.

[input]solve(x^2+y^2=169,0.5*x*y=30)[/input]
[input]solve(sqrt(169-x^2)=y, 0.5*x*y=30)[/input]
[input]solve(sqrt(169-x^2)=y, y=1)[/input]
[input]solve(sqrt(169-x)=y, y=1)[/input]
[input]solve(2*-3*z=4, -y+7*z=-12)[/input]
-------------------------------------------------------------------------------------------------------------------------------------------------------------
Alright, I have probably established that the Web2 calc is not great for this, let's look elsewhere.

I used "Desmos Graphing calculator" to get this answers. This is a free online calc.
With this calculator I had to cut the circle in 2 and do it in 2 halves. This is because Desmos (and many other calculators) can only deal with functions. A circle is not a function. So it has to be split into a top half and a bottom half.
highlight the web address, right click and choose 'goto'
https://www.desmos.com/calculator/r3xe8e3rn5

I also used 'WolframAlpha',another free online calculator, which is probably a better choice for this question.
https://www.wolframalpha.com/input/?i=x%5E2%2By%5E2%3D169%2C+0.5xy%3D30

I hope that helps

MelodyMar 19, 2014

+118725

mina:
:? 0.2 over 100 times 700

0.2/100*700

MelodyMar 19, 2014

+118725

Guest:
if i am make 200 invites that are 5x7 how many feet of paper do i need

I think 5 by 7 inches would be more realistic Kitty. (Don't forget to do reasonableness checks )

200*5*7 = 7000 inches ²

12*12 = 144 square inches in a square foot

7000/144 = 48.61repeater

So you will need about 49 square feet of paper.

MelodyMar 19, 2014

+5478

Hi joshua,

Displacement of an object is the overall change in distance from its starting location.
Therefore, since the object is traveling 20km south, then 11km south again,
the total distance south would be 20+11
= 21km south

Same with the 9km west and 3km west.
The total distance west would be 9+3
=12km west

Therefore, the displacement of the object would be 21km south, 12 km west. It is in whole numbers.

I don't know what the answer would be in degrees, but this site might help:
http://www.dummies.com/how-to/content/how-to-calculate-the-displacement-of-an-object-mov.html

kitty<3Mar 19, 2014

+5478

Hello cheetah970,

Yes, there is. I haven't tried this, but the administrator posted it a long time ago. Here is the link:
http://web2.0calc.com/questions/systems-of-equations

For the equations:
2y-3z = 4
-y + 7z = -12

You would put in something like this:
solve( 2 * y - 3 * z = 4 , - y + 7 * z = - 12)

But I tried your equation, and strangely it doesn't work. Maybe it is a typo?
Sorry I couldn't help a lot; maybe when Melody or some of the other people come on they may be able to help you:)

kitty<3Mar 19, 2014

+5478

Hello Pirateson3,

There is a calculator on this site:
http://web2.0calc.com/

I'm sure that it'll answer your question:)

kitty<3Mar 19, 2014

+5478

Hi timmy,
So you would use the Distributive Property for this one:

10(2a+5)

Distribute the 10 into (2a+5)
=10*2a + 10*5
Then multiply it out.

=20a + 50

kitty<3Mar 19, 2014

+130561

I'm pretty sure Melody is correct!!

To see this further, here's what I used to tell my students when I was tutoring::

Assume - if we could do so - that we are going to take ALL the sets that we can make by choosing ANY 7 marbles out of the 200, and we're going to lay all these sets on the ground.
The number of these sets = C(200, 7).

Now, I'm going to walk around and pick up certain sets. But the only ones I'm interested in are the ones that contain 3 red marbles and 4 blue ones. Now, in each set I have seven "slots."
The first 3 slots will contain red marbles and the last 4 will contain blue ones. Note that the order of marbles really doesn't matter - one ordering is as good as any other.

Well, the number of total sets I can make consists of two subsets of things in each set of seven marbles - namely, choosing any 3 red marbles from 25 and choosing any 4 marbles from 175.. So, the total number of ways to do this is just [ C(25,3) * C (175, 4)].

So, the total probability = [The number of sets of things we're interested in picking up] / [The total number that were laying on the ground before we picked any of them up]

And, as Melody's numbers attest, this is just [ C(25,3) * C (175, 4)] / [C(200,7)] = 3.8%

CPhillMar 19, 2014

+118725

cole:
what are the roots of 2x^2+3x-7=o

Please also look at this old posts. It will direct you to you tube. It will help.

http://web2.0calc.com/questions/quadratic-formula-do-you-have-trouble-remembering-it

MelodyMar 19, 2014

+5478

if i am make 200 invites that are 5x7 how many feet of paper do i need

Well, first that depends on what unit the 5x7 is. I'm assuming that is in feet.

Then, find 5*7, which is 35. So each invite is 35 feet squared.
Then, multiply this by 200 to find the total square feet of paper needed.
200*35

=7,000 square feet of paper total (only if all your starting units were feet.)

kitty<3Mar 19, 2014

+118725

Ippo:
There are 6 girls and 4 boys. They all participate in a lottery for the places in a line. With which probability will the boys be last in the line and why?

Do you meant that all th girls are first and all th boys are further back?

Probability is not my forte either, but

I think that there are 10!/(6!*4!) = 210 ways of arranging the boys and the girls in a line. I am considering all the girls to be the same and all the boys to be the same since I only care about their gender.

There is only 1 way fo all the boys to come last .

So the probability is 1/210

I'm reasonably sure that is right - now i will compare it to CPhill's answer. YES it is the same. GREAT.

Do you understand Ippo?

MelodyMar 19, 2014

#96

[color=#BFBF80][color=#BFBFFF][/color][/color]

Melody:
hi everybody,
Who's up for a challenge? I chose these numbers at random.
PUZZLE 1
3,5,7,2,100,and 50.

Use these numbers to make the number 953.

Rules:
Use only these numbers
No number can be used twice
You do not have to use all the numbers
You can use + - x or divide.
You can use brackets.

First one to respond with exact answer wins. If you post later but you have a substantially different answer, you win too.
If no-one gets the exact answer then closest answer after 12 hours wins. (competition closes in 12 hours)

You will be expected to explain how you got your answer.

Use a name other than 'guest' and your wins will be recorded.
If enough people are interested we will keep playing with different numbers.
Any questions?
(I have copied this game from the TV show 'Letters and numbers')
Have fun.

GuestMar 19, 2014

+118725

70R573N:
Suppose U is a population consisting of 200 marbles in which 25 of them are red. What is the probability of getting 3 red marbles in a sample of 7?

If you had a great many more marbles and 25/200 = 1/8 were red then this would be a much mor standard problem. Because each time a marble is chosen i could say that the chance of getting a red one is 1/8. the events would be independent of one another.

If that were the case then the probability of getting 3 reds would be 7C3 * (1/8) ³ * (7/8) ⁴ = 35 * (1/8) ³ * (7/8) ⁴ = 0.04007101 = about 4%

--------------------------------------------------------------------------------------------------------------------------------------------
[size=150]Let me think about the real question.[/size]

How many ways can 3 red and 4 others be chosen 25C3 * 175C4
How many combinations of 7 are there altogether 200C7

Probability = 25C3 * 175C4 / 200C7 ==> 0.038019 ==> about 3.8%

I think that maybe 3.8% is the right answer but I am not very good at probability so I want another mathematician to look at it.

SOMEONE ELSE - PLEASE TAKE A PROPER LOOK - I WANT TO KNOW HOW TO DO THIS TOO - Melody

MelodyMar 19, 2014

+118725

Mandl:
What is 5 to the power of 3

5^3 = 5 ³ = 5*5*5 = 125

MelodyMar 19, 2014

+118725

marczoro:
:? how do you calculate big numbers
for an example would be like this
24-94*90/93

Is this what you mean? I just did it with the site calculator.

24-94*90/93

MelodyMar 19, 2014

+118725

Guest:
15*13

Do you want 15*13 or 15*3
Either way you can use a calculator- there is one on this site.

MelodyMar 19, 2014

+118725

7749PX8CE:
Shawna opens a bank account with $400. The account accrues 8% interest compounded annually.

How much money, to the nearest cent, will she have in her account at the end of 4 years? (Use the formula A=P(1+rn)nt, where P= initial amount of money, r = interest rate, t = the number of years, and n = number of times the interest is compounded per year.)

Almost but not quite Sam

P is the principle = 400
r=0.08 and n=1 because it accrues just once a year.
t=8 because it is 8 years

The formula is not A=P(1+rn)nt it is A=P(1+rn)^(nt) or A=P(1+rn) ^nt

To get the nt up in the air, I highlighted it and then pressed 'sup' which is found above the smilies. sup stands for superscript.

A = 400*(1+0.08) ⁴ ==> 400*1.08 ⁴

MelodyMar 19, 2014

+118725

i love math:
:shock: two thirds of nine

CPhill has given you a very good pointer.

This site might help too.

http://www.mathsisfun.com/fractions_multiplication.html

MelodyMar 19, 2014

+130561

Thanks for your reply.

Yep....I should have "streamlined" it, but.....I was really thinking "out loud" to myself while I was typing!! (LOL!!!)

This problem IS "simple," but it just doesn't seem so at first, does it??

Glad I could help!!!

CPhillMar 19, 2014

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