Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
mehr ..

Melody 02.04.2022

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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. mehr ..

Melody 16.03.2022

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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 mehr ..

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Melody 15.03.2022

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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

Off-Topic

Melody 13.03.2022

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WELCOME BACK CPHILL !

Melody 11.02.2022

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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. mehr ..

Melody 01.02.2022

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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 mehr ..

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Melody 09.01.2022

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HAPPY BIRTHDAY CHRIS!

Melody 20.12.2021

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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 mehr ..

Off-Topic

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Melody 04.11.2021

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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

Off-Topic

Melody 29.10.2021

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a and B are acute angles in quadrant 1, sin a= 7/25 : cos B =5/13. Without using a calculator determine the values of: Sin(a+B) and tan(a+B).[/size]

Look here.

http://gyazo.com/86a75edbd43609dd8cd27e67f1291d52

You are probably supposed to memorise the first 3.

Melody04.12.2013

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1/2x - 5 + x -10 = 3x/2 - 15

Melody04.12.2013

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0.16 = X/100 How to make a decimal into a fraction then percentage

0.16 = 16/100 = 16%

Melody04.12.2013

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i cant solve
y=(1/4)X2
Y=3

Do you mean ?
y=(1/4)x ²
y=3

3 = 1/4 * x ²

12 = x ²

x = + or - sqrt(12)

x= +- 2sqrt3

Melody04.12.2013

+118725

0

2.29=cos(x)

Hi Special,
The cos of an angle has to be between -1 and 1
so next time you should see straight away that the question is not correct.

Melody04.12.2013

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0

Josie's checking account balance is 535.23. She deposits a check for 97.83. She then writes a check for 299.98 for a new bicycle and uses her credit card to withdraw $40.00. What is the net change in Josie's account?

Hi Mathicorn and Someone special. (You are special, everyone is)

Special, you have found out how much money is in the account but that was not the question.
The net change is +97.83 - 299.98 - 40 = -242.15

Melody04.12.2013

+118725

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Yes, Pi is an irrational number which means that it cannot be written exactly as a fraction or a decimal. It cannot even be writtne exactly as a repeating decimal.
The digits after the decimal point just keep going on forever without even forming a pattern.

Melody04.12.2013

+118725

0

I have this equation:
2 = sin(x) - cos(x)
How do I find x?

Hi Kytuzian,
-1 < sin(x) < 1
-1 < cos(x) <1

So the only way that this would work would be if sin(x)=1 and Cos(x)=-1
but when sin(x)=1 cos(x)=0 and when cos(x)=-1 sin(x)=0

So there are no solutions.

Melody04.12.2013

+118725

0

Hi SerJibblenits

The Probability that Azher, who always walks to work, arrives late on any day is 0.11. Calculate the Probability that, during a period of 20 working days, he is late on exacalty 4 days.

I'll not only show you the working I will also do my best to explain.
First you must understand that this answer assumes that the chance of being late on any day is indepentant of any his timeliness on any other day.

Prob of being late = P(a) = 0.11
Prob of not late = P(a with a bar on the top) = 1 - 0.11 = 0.89
The probability of being late for the first 4 days and then not late for the next 16 days would be 0.11^4 * 0.89^16 = 2.2689 * 10^(-5) (to 5 significant figures)

Trouble is, he might be late on the 2nd, 5th 16th and 19th day
or he might be late on the 10th, 11th, 14th and 20th day etc
You need some way to work out how many combinations of 4 days you can choose from 20 days.
And this formula will do it fo you
20C4 = 4845
(There is an nCr button on your calculator)

So the probability that he will be late on exactly four days will be 20C4 * (0.11^4) * (0.89^16) = 0.1099 (correct to 4 dp)

Melody04.12.2013

+118725

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Hi Rosey,
The translation did not make a lot of sense.
Did you mean:
A cliff is 40 feet high.
A car drives off the top of the cliff at 10 miles per hour.
How far from the base of the cliff will the car land?

Bing Translation

Hola Rosey,
La traducción no hizo mucho sentido.
¿Quisiste decir:
Un acantilado es de 40 pies de alto.
Un coche conduce a la cima del acantilado a 10 millas por hora.
¿Qué tan lejos de la base del acantilado el coche aterrizará?

Melody04.12.2013