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

-10

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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

+118691

0

Okay Random
I will try.
Let's just look at the first question.
Jo invested some money is invested at 7.2% per year. It is compounded every 2 months for 8 years.
a) Write 7.2% as a decimal
b) How many lots (nets) of 2 months are there in a year . Use this number to get the next 2 answers.
c) r is the interest rate per compounding period Find r (show working)
d) n is the total number of compounding periods. Find n (show working) and put n=

Now I think that you can do Part a. Do you know how to change a percent to a decimal?

Even if you can't you can still try to follow what I am saying below and hence answer part b

The rest is like the banana question.
Think of a year as a dozen months
Think of the months like bananas (12 bananas in a dozen - 12 months in a year)
The months are in 'nets' of 2 just like the bananas were.
So you should be able to work out what I am trying to say for part b)

Do these 2 parts and then get back to me with your answers.

If you have a sudden brain wave (which you might) you can try the next to questions as well.
The logic is very close to the nets of bananas.

Melody3 Jan 2014

+118691

0

Ok I'll try but I'm not sure you are ready yet.
Show all your working. Do each question carefully with full working before you move to the next question.

Jo invested some money is invested at 7.2% per year. It is compounded every 2 months for 8 years.
a) Write 7.2% as a decimal
b) How many lots of 2 months are there in a year . Use this number to get the next 2 answers.
c) r is the interest rate per compounding period Find r (show working)
d) n is the total number of compounding periods. Find n (show working) and put n=
----------------------------
e) What is the compound interest forumula, (n and r are little letters)
f) Substitute in the values of n and r into the equation. (you are more likely to get this correct if you put the final value of n and r in - don't try to put the working in)
(you can also simplify the equation as a next step)
----------------------------
g) If the original amount of money was $5000 what has it grown to? show the substitution into the formula.
h) How much interest has Jo earned? (to the nearest cent)

Good luck and don't try to cut corners.

Melody3 Jan 2014

+118691

+3

Thanks Kitty, that's great!

Now our score is
gb4242. (1 win - 10points)
Jedithious (1 win- 10 points)
Kitty (1win - 10 points)

Kitty, would you like to post the next numbers ?
(You can check it works first if you want to and you can answer yourself if no-one else answers with in 2 hours.)
If you just want to make the numbers up randomly that's fine, I will check them. If they don't work or if I think that they are too difficult I'll change them a little or give a hint. Does that sound alright to you?
If you post the numbers let me know if you have checked them already.
If you want to change to a different game that's okay too. Just tell us what we have to do.

Melody3 Jan 2014

+118691

0

Guest:
Guest:
How do you substitute .05m+20+20=.10(m-100)+15+20

Start by simplifying each side individually and then show me what the question has become.
(I mean, expand the brackets and collect the like terms.)

Melody3 Jan 2014

+118691

0

Lolitu:
Sqrt3*( 6x-5) +2=-3

You need to get everything except the x off the LHS.
You can start by subtracting 2 from both sides. (What you do to the left side you must also do to the right side)
So you now have got rid of the +2
Now think about what you can get rid of next.

Melody3 Jan 2014

+118691

0

me.aciamaj:
[center][/center][/center]A dog house is 4 ft.wide and has walls 2 ft. high. If the pitch of the roof is 45degrees, how high is the dog house in the center?

this is probably an easier question than you are thinking.
You don't need trig or pythagoras.
Draw a cross section of the kennel and think about it.
Hint: Think about the properties of the triangle that is on the top.

Melody3 Jan 2014

+118691

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Asha:
x+1=sqrt(x^2+x+7)

Start by squaring both sides. Then it will fall out very easily.

Melody3 Jan 2014

+118691

0

adam:
whats 4x*(2018/pi)*44

Why are you having a problem with this Adam?
It is the same as

(4 * x * 2018 * 44) /pi

does that help??

Melody3 Jan 2014

+118691

0

duck908:
Can someone help me create a formula with the following input/output table?
input (x)/output (y):
50/1.050
100/1.250
150/1.450
200/1.650
250/1.850
300/2.005
350/2.250
400/2.450
450/2.650
500/2.850

You start by looking at the xs and ys separately.
The xs are going up by 50 every time. The ys are going up by 0.2 every time.
This should be enough to tell you that it is the equation of a line. (The gradient will be the same between each pair of points)

---------------------------------------------------------------------
Once you recognise it as a line you could just use any 2 points and use the line between 2 points formula to get the equation.
That would probably be the most sensible thing to do.
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I usually do it a different way.
Now I am going to talk about a multiplying factor, which is the gradient.
and a number that is tacked on the end, which is the y intercept. (I'm going to call it b)
Since the xs go up by 50 each time, and the ys go up by 0.2 each time
50 * the multiplying factor =0.2
The multiplying factor (gradient) = 0.2 / 50 = 4 * 10 ^-3 = 0.004
so
y = 0.004x + b
Sub in one of the points say (50, 1.05)
1.05 = 0.004 * 50 + b
1.05 = 0.2 + b
b = 1.05 - 0.2
b = 0.85

so
y = 0.004x + 0.85

This is similar to what admin got only they forgot to divide by 1000
y = 4x/1000 + 850/1000
y= (4x + 850) / 1000

Melody3 Jan 2014

+118691

0

Do you have 4 specific points?
there might be a better way but i would try to do it as a locus question.

the distance between 2 three dimensional points is
sqrt[ (x ₂-x ₁) ² + (y ₂-y ₁) ² + (z ₂-z ₁) ²]

You have got your 4 points plus you can let the centre be
(x _c,y _c,z _c)

So the distance from each of the four points to the centre would have to be equal.
I'd set up the 4 equations and if they looked too difficult to solve myself I'd try to solve them with an online calculator . (to find the centre)
Once you have the centre, you can work out the radius.
Then you can write down the formula of the sphere. (All you need is the centre and the radius)

Melody2 Jan 2014