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

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the diagram shows a cross section of a circular washer of radius, 2.8 cm with a rectangular hole of length,3 cm and breath,2.5 cm.Find the area of the cross section of the washer

the circle minus the rectangle.= pi*r*r - (3*2.5) cm squared

MelodyNov 1, 2013

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16+25 - (2*20*CosC)=36

42- (40cosC) = 36

6 = 40cosC

6/40 = cosC

cosC = 0.15

inverse cos 0.15 = 81.37 degrees

It is really good that you recognised that you needed an angle bigger than 60degrees.
Can you work out what you have been doing wrong?

MelodyNov 1, 2013

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if 16+25+-2(20)CosC=36 , what is the angle measure of C ?
Before you even start you need to make sure you calculator is in degrees or radians - whichever one you need

Why are you confused ?

It would be more helpful if you put the brackets like this, you will be less likely to make mistakes.

16+25 - (2*20*CosC)=36

Once you solve for CosC then put the answer in you calc and press inv cos to get the value of C

Is that enough help?

MelodyNov 1, 2013

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I just couldn't leave it alone.

What is the largest integer N such that 7^N = (1000!)/(500!)^2?

I experimented with 20!/(10!10!) with 3^N
and 30!/(15!15!) with 3^N
If you experiement with thes smaller ones hopefully you will be able to see where I got my logic from.

and this is what I came up with
numerator
1000/(7^1) = 142 (i don't care about the left overs)
1000/(7^2) = 20
1000/(7^3) = 2
1000/(7^4) = 0
Add them all up and you get 164 So 7^164 is a factor of the top

denominator
500/(7^1)= 71
500/(7^2)= 10
500/(7^3)= 1
500/(7^4)= 0
add them up and multiply by 2 = 2*82 = 164 so 7^164 is a factor of the bottom

When you cancel all the 7s cancel out and you get 1
So the biggest power of 7 is 0. (It is not divisable by 7)

I am pretty sure that is correct.

MelodyNov 1, 2013

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This question is making my mind boggle.

I suggest that you try doing something very similar only with much smaller numbers and see if you can make sense of it that way.

Maybe you have already done this.

I haven't given up on it but I have other things to do now.

MelodyNov 1, 2013

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What is the largest integer N such that 7^N = (1000!)/(500!)^2?

I think there is something missing.
You only have one unknown and an = sign therefore there is just one answer.
maybe it should be > or < ?

Also, (1000!)/(500!)^2 is a huge number. I've tried to do it on a couple of calculators and they just give error messages or do nothing at all. I've never seen that before. I am assuming that they just won't handle factorials of this size. The question can still be answered but not simplified.
This might not matter if the question is a bit different.

MelodyNov 1, 2013

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how do I determine the mass of :3.01 x 10^23
You have no units so you can't.

MelodyNov 1, 2013

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Already answered this for Howdy.

MelodyNov 1, 2013

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tan(x/2)=sin(x/2)

sin(x/2) / cos(x/2) = sin(x/2) / 1

cos (x/2) = 1

x/2 = 0, 2pi, 4pi,6pi, .....

x= 0, 4pi, 8pi, 12pi,

so x = 4n*pi radians where n is any integer

you can do the degrees yourself.

MelodyNov 1, 2013

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A mixture of 12% disinfectant solution is to be made from 10% and 17% disinfectant solution. how much of each solution should be used if 14 gallons of the 12% solution are needed?

I don't think the question is quite complete.

I will assume for starters that you have lots of the 17% solution and you can make it all up from that.

There is a really simple formula for this

Amount of strong concentrate needed = concentration wanted / concentration availble * amount that you want to make up

Amount of strong concentrate needed = 12% / 17% * 14gallons (the percent signs can just be cancelled out)
= 12/17*14
= 9.88 g (to 2 dec places)
Then you will have to add (14-9.88) 4.12 gallons of water.

If you use the 10% mixture you will have to add some of the 17% mixture as well or it won't be strong enough.

MelodyNov 1, 2013