Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
और पढ़ें ..

Melody 2 Apr 2022

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Reporting problems.

There are a number of people having problems at the moment.
If you lodge an error can you please give all relevant information that you can think of.
Where you are in the world - the city or the country - is often very important information. और पढ़ें ..

Melody 16 Mar 2022

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How to make an empty rectangle in Latex

I just worked out how to make an empty box of various horizonal size easily in LaTex.
This is not a recommended method, but other methods that I have tried here have not worked.
This coding is really simple. Just put letters inside और पढ़ें ..

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Melody 15 Mar 2022

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HAPPY ANNIVERSARY CHRIS! (CPhill)

I just realized that you became a member here exactly 8 years ago today!

It has been great to have you here all that time

और पढ़ें ..

विषय से परेे

Melody 13 Mar 2022

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WELCOME BACK CPHILL !

Melody 11 Feb 2022

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Very interesting question. No high level maths required.

This question was posted a couple of days ago.
https://web2.0calc.com/questions/geometry_73561

I think it is really interesting. It looks much more difficult than it really needs to be. और पढ़ें ..

Melody 1 Feb 2022

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Members have a better experience. Their questions get more attention.

Almost everyone is posting as a guest.
If you post as a member your questions will have a far greater chance of a timely and helpful response.
If you are a genuine learner and interact with us, you will become known and answerers will do और पढ़ें ..

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Melody 9 Jan 2022

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HAPPY BIRTHDAY CHRIS!

और पढ़ें ..

Melody 20 Des 2021

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Some guidelines for question askers.

Please note:
1) Ask only one question per post.
2) When asking a question talk about what you have tried for yourself. Then people will take you more seriously and will be more able and willing to help.
3) If you get an answer और पढ़ें ..

विषय से परेे

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Melody 4 Nov 2021

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Remeniscing - a little historical humour.

I just found this old post that some of you, who have been around for a while, might find amusing.

https://web2.0calc.com/questions/look-at-the-new-leader-board

विषय से परेे

Melody 29 Okt 2021

+118690

0

Second interpretation, which now I think about it is the same thing (as n approaches infinity) so it is a good thing that I got the same answer.
131219 latex limit question2.JPG

Melody19 Des 2013

+118690

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What do you think of this answer?
131219 latex limit question.JPG

Melody19 Des 2013

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hi Narciss,
It is really nice to interact with you in real time.

lim(x->inf.) ((1-3/4+9/16-27/64..)*n^2)/(n^2-1))

Firstly, shouldn't it be n->inf because there are no x's in the expression?

Also I am struggling a little with this (1-3/4+9/16-27/64..) if the dots mean that it goes on for ever no matter what x (or n) is, then, it is the infinite sum of a geometric progression
which is T ₁/(1-r) = 1 / (1- (-3/4)) = 4/7

or is it really meant to be (1-3/4+9/16-27/64....(-3/4) ^(n-1)) in which case it would be the sum of a geoopmetric progression

Sn = T ₁(1-r ⁿ)/(1-r) = 1(1-(-3/4) ⁿ)/ (1- (-3/4)) = (1-(-0.75) ⁿ)* (4/7)

You are right this poor maths presentation is making it difficult. I can write it up properly in maths speak (Latex) and import it if we decide it is really necessary but it does take quite a while and it is late in Australia so I am not over keen at present.

Anyway, would you like to comment on the 2 possible interpretations of the sequence. Which one do you want?

Melody19 Des 2013

+118690

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Do you understand how yoyoman did all this or do you need some explanation?

If the circles just touched then the distance between their centres would be exactly equal to the sum of their radii.

This is not the case, can you tell me (with explanation) if they overlap or if they don't touch at all?

Melody19 Des 2013

+118690

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Narciss:
lim(3/4)^(n-1) = ?
n->inf.

Hi Narciss,
I can 'see' that the answer is 0.
This is because 4 to the power of some huge number is going to be much bigger than 3 to the power of the same huge number, and as that number gets even bigger the difference will become more and more extreme.

Melody19 Des 2013

+118690

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mario franco:
if a house depreciates at the rate of 2.5 percent per year for 10 years and has a present value of $12500 , what was the original value of the house?

Our guest was close - but no candy cane, sorry. It was a really good try though.

Let's think about this one
Let the original price be $A (which is 100% of A)

After 1 year it will depreciate by 2.5% of A
So its new value will be 100% of A - 2.5% of A which is (100-2.5)% of A => 97.5% of A => 0.975A

So original value = A
after 1 year A*0.975 dollars
after 2 years A * 0,975 * 0.975 = A * 0.975 ²
...
after 10 years what do you think it will be? but you know that after 10 years it is $12500.
So set up an equation and solve it.
Maybe you could also think about what formula you could of used in the first place.

Melody19 Des 2013

+118690

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Stargal411:
please help, I need it in decimal form but I cant figure it out, if u can solve it, or recommend a calculator website that can solve it in decimal form, then please do, I desperately need this.

The opposite of cube is cube root and cube root is a power of 1/3 so

[x ³] ^1/3 = x

this works for other powers too like

[20 ⁷] ^1/7 = 20

[13 ^1/4] ⁴ = 13

[x ^1/5] ⁵ = x

Now inequalities are solved in a very similar way to equations (if you mult or divide be a neg no. you turn the sign around but that's not relevant here.)
Like with any equation, what you do to one side you must do to the other side as well, or in this case, both other sides.

72< x^3 < 19

72 ^(1/3)< [x^3] ^(1/3) < 19 ^(1/3)

And you can finish it

Melody19 Des 2013

+118690

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Stuck34:
24 Divided by (__ X 2) = 4??

I suspect that you are a little kid (maybe 6th class? Please don't be offended if I am wrong) so,

I would just say
24 divided by "what" = 4

This means 24 lollies divided between how many children would give each child 4 lollies.

I want you to get that answer for me and then we can talk about the rest of the question.

If you want to think further by yourself the next question is this number you just found is split up into 2 times "a new number".
That new number is the final answer to the question.

You can check it on your calculator (or on paper)
24 divided by (answer x 2) = If your calculator says 4 then you know your answer is correct.
If you put this in a calculator don't forget the brackets.

Melody19 Des 2013

+118690

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mathguy007:
x^2-10x+y^2-20y=-125 what is x+y=?

Please help, Thanks!

David is correct in everything that he said.
I just thought I would comment because you actually didn't need to recognise all that.
You do need to complete the squares.
that is
x ²-10x +y ²-20y = -125

x ²-10x +25 +y ²-20y +100 = -125 +25+100

(x-5) ² + (y-10) ² = 0

(x-5) ² = - (y-10) ²

now the left hand side is a square so it has to be positive
the right hand side is a neg * a square so it has to be negative.
The only way that this can make any sense is if they are both 0
so x-5=0 and y-10=0
x=5, y=10

x+y = ?

Melody19 Des 2013

+118690

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kimhorrill:
How do I calculate a Zobt?

z = (score - mean) / stardard deviation

http://en.wikipedia.org/wiki/Standard_score

Melody19 Des 2013