Melody

921 Questions
34315 Answers

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Mathigon website

I just discovered a site called mathigon

https://mathigon.org/dashboard
read more ..

Melody Apr 2, 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. read more ..

Melody Mar 16, 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 read more ..

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Melody Mar 15, 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 Mar 13, 2022

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WELCOME BACK CPHILL !

Melody Feb 11, 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. read more ..

Melody Feb 1, 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 read more ..

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Melody Jan 9, 2022

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HAPPY BIRTHDAY CHRIS!

Melody Dec 20, 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 read more ..

off-topic

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Melody Nov 4, 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 Oct 29, 2021

+118725

0

If 1/2x +1/2(1/2x + 1/2(1/2x +1/2(1/2x + ... = y,
then x = ?

This one made me think.

If you start multiplying it it out you get
1/2x + 1/4x + 1/8x ........= y

x ( 1/2 +1/4 +1/8 + .........) = y

now
1/2 + 1/4 + 1/8 + ...... is the infinite sum of a GP with a=1/2=0.5 and r = 1/2 = 0.5

limiting sum = a/(1-r) = 0.5 / (1-0.5) = 2
so
2x = y
x = y/2

MelodyNov 21, 2013

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0

I did it on my calculator and got 1.55 * 102 ⁷ (correct to 3 sig figures)

so the leading digit is 1

is that what you meant?

MelodyNov 21, 2013

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0

What is the slope of the line represented by the equation
-2y=x-1

Divide both sides by -2 to get y by itself
then
the slope (gradient) is the number that x is times by.

MelodyNov 21, 2013

+118725

0

A cone is a 3 dimensional figure. It doesn't have a perimeter.

MelodyNov 21, 2013

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0

If x=0 what does y equal?
If x=1 what does y equal?
If x=1 what does y equal?

Now you have 3 points so you can plot them on your number plane and join them together with a long line (with arrows on the ends)

MelodyNov 21, 2013

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0

10^x=2.99 express the solution in terms of log

log ₁₀10^x=log ₁₀2.99

x=log ₁₀2.99

MelodyNov 21, 2013

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0

http://www.youtube.com/watch?v=zZWd56VlN7w

mean of 56.3% and a standard deviation of 8.1%. in what percent of the game will the success rate be between 50% and 60%
(I am assuming that the scores are normally distributed(

Z ₁ = (50-56.3)/8.1 = -0.77778

Z ₂ = (60-56.3)/8.1 = 0.45679

Probability that -0.7778 < Z < 0.45679

is give by the area under the normal curve and you have to read it off your z score tables. You will do one side at a time.

The you tube clip above may help you.

MelodyNov 20, 2013

+118725

0

use pythagoras's theorem

MelodyNov 20, 2013

+118725

0

sin(x)=12/9

You got an error on your calculator when you tried to do this, didn't you?

sinx = opposite / hypotenuse
What is the longest side on a right angled triangle?
what does that tell you about this fraction?

Can you work out where I am going here?

MelodyNov 20, 2013

+118725

0

if someone jumps off a 10.0m high tower, what will their velocity be when they reach the water?

I am going to assume no air or wind resistance and the guy falls (not jumps)
The initial height is 10, the end height is 0

Initially
y''=-g
y' = 0
y=10

ongoing
y'' = -g
y' = -gt
y = -gt ² / 2 + 10

when y=0
0 = -gt ² / 2 +10
....
t = sqrt20 / sqrtg
so
y' = -g * sqrt20 / sqrtg

y' = - sqrt(20g)

If g is approx 9.8m/s ² then y' is approx = -14

So at impact the speed will be 14m/s

MelodyNov 20, 2013