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# Fun math thing: how big will the rolled madrass be?

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So when planning for a camping trip, I ended up wondering how one calculates the diameter of a rolled camping madrass will be when you know the length,height (and width) of the flattened madrass.

What I find fun is that I had it in the back of my back a few days, never actually sat down to analyze, till I found the solution. Of course waaaay easier (and even straight forward once one properly thinks about it) than I ever thought at first ðŸ™‚

Not spoiling you the fun, but for dimension 2*200*80 answer is 15.96

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Of course assuming no air in the rolled layers

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I get 22.56 cm and since you didnâ€™t show your work, Iâ€™m not showing mine.ðŸ˜Š

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This asks for it:
YOu show me yours I show you mine :D:D:D:D

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Mine is:

Get area of side of madrass then find radius of circle with same area.

so 2*200=r^2*2pi -->r=(200/pi)^(0.5) --->
>>> np.sqrt(200/3.14)
#7.9808688446762215

But asked ofor diameter so:

>>> np.sqrt(200/3.14)*2
15.961737689352443

Â

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Ok you win, long time no geometry I guess. Area of circle is pi r^2 not 2pi r^2...

So I also get:
22.573305919324014

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What do I win?

Â

By the way, since you are an admin can you please look into why LaTex formulas do not render here?

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Not sure how to fix it, did not find usefull stuff in adminCP, but am no guru at this

Â

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• 3 months later...

"madrass"= "mattress" in what language?

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• 2 months later...
On 1/4/2021 at 9:39 AM, CountryBoy said:

"madrass"= "mattress" in what language?

Oh, I see, it is a matress in Madras!

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