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[sturdy quarry]

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[summer mauve]

H=4 inch r=2.5 inch

Calculate the volume of hollow cylinder

[weary hornet]

k 1 sec

what does outer diameter mean?

is there a formula to find the volume of a hollow cylinder?

or do you find the volume of the whole cylinder then the hollow part and subtract

[summer mauve]

There is a formula to find the volume of hollow cylinder

π (R² -r²)h

I think the outer diameter/2 is capital R and thickness is small r

[weary hornet]

R = 5, r = 1.5?

[summer mauve]

R=2.5

[weary hornet]

why 2.5

o shit

its radius

not diameter

mb

?

[summer mauve]

Yes

Now find the cost of 1 toilet paper

[weary hornet]

so the volume of 1 tp is 6pi

[summer mauve]

Now divide cost of 1 tp and volume of the the tp

This will get us cost per cubic meter

[weary hornet]

?

[summer mauve]

I think that's right

[weary hornet]

but its supposed to be that $1 = 80 in^3

[summer mauve]

Well we clearly went wrong somewhere

[weary hornet]

oh i think i know

[summer mauve]

Really?

[weary hornet]

should be 0.75 and not 1.5

because 1.5 is the internal diameter

[summer mauve]

Oh right

[weary hornet]

wait no that doesnt work

1.5 is the thickness

not the internal diameter

[summer mauve]

But thickness is the diameter

[weary hornet]

no

that part is thickness

the external diameter is 5

[summer mauve]

Yep

[weary hornet]

then the thickness is 1.5 on both sides

[summer mauve]

Ok I guess we were on the right track

[weary hornet]

so 5-1.5*2

is 2

so the internal diameter is 2

and the internal radius is 1

[summer mauve]

Right that maybe the answer

[weary hornet]

like this i think

[summer mauve]

I think this is right too

[weary hornet]

ok i think this is good

[summer mauve]

Ok

Good work

You didn't need my help at all

[weary hornet]

yeah i did

it helped

i didnt really know what to do to start

so thanks

🙂

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