1. ## Stupid Math ...

Got a cylinder with no top.
250 square cm's of fiberglass.

r cm's would represent the base radius of this cylinder. What is the cubic function? What are the dimensions of the cylinder when it has 200mL in it? Not only what is it, how did you get it ... this could really come in handy later on for me.

I was thinking along the lines of V=pir^2h ... C=2r ... = 2pir+pir^2 ... whaaaaat the ...

What this has to do with boxes ... you shall see.

Much appreciated.

- Steve

2. ## Re: Stupid Math ...

And if you don't know the height, or any dimensions ... where I'm confused.

- Steve

3. ## Re: Stupid Math ...

I need to know the cubic function of a cylinder with no top made out of 250 cm^2 of fiberglass, or metal, whatever. First of all.

- Steve

4. ## Re: Stupid Math ...

Originally Posted by Jmac
You don't know any dimensions, but you need a cylinder to handle 200 mL ?
so screwed. steve if u get boggled up, i took geometry last year (passed wit a 91) but i'm sure u know what ur doing. :veryhappy

5. ## Re: Stupid Math ...

Originally Posted by jbl_marshall21
so screwed. steve if u get boggled up, i took geometry last year (passed wit a 91) but i'm sure u know what ur doing. :veryhappy
So this guy makes a can with 250cm^2 of metal, fiberglass, whatever ... with no top.
So you let r cm's represent the base radius. What is the volume of the can as a cubic function of r ?

Im really confused.

- Steve

6. ## Re: Stupid Math ...

you want a function for the volume of the cylinder with a surface area of 250 cm^2... it's a **** good thing I understand Stevenglish...

7. ## Re: Stupid Math ...

Originally Posted by Wonderbread
you want a function for the volume of the cylinder with a surface area of 250 cm^2... it's a **** good thing I understand Stevenglish...
Yeah well thats as good as it gets

- Steve

8. ## Re: Stupid Math ...

not sure if this is right...
you never know, lol.

V = (Pi*r^2)[(250-Pi*r^2)/p]

Pi = Pi...
r= radius
p = perimeter

9. ## Re: Stupid Math ...

Originally Posted by ss3079
So this guy makes a can with 250cm^2 of metal, fiberglass, whatever ... with no top.
So you let r cm's represent the base radius. What is the volume of the can as a cubic function of r ?

Im really confused.

- Steve
SA=250cm^2

thats without a top. hmmm tricky let me think here. aah yes nah nevermind i can't remember the the surface area formula of a cylinder.

its right on the tip of tounge. ****'t if u don't figure it out tonight i'll get it tomorrow. i'll see if my math teacher can get it cuz i don't remember the **** formula. wait is it circumference X height + the area on the bottom?

10. ## Re: Stupid Math ...

Thanks much ... we'll see if it works.

- Steve

11. ## Re: Stupid Math ...

Originally Posted by Wonderbread
not sure if this is right...
you never know, lol.

V = (Pi*r^2)[(250-Pi*r^2)/p]

Pi = Pi...
r= radius
p = perimeter

perimeter on a cylinder????????

12. ## Re: Stupid Math ...

Who knows, I'm pretty confused right now ...

A can with no top is made from 250cm^2 of fiberglass. 'r' cm's would rep. the base radius of the can. Need the volume of the can as a cubic function of 'r'.

I've gotten things scribbled down here ...
SA= 250cm^3 = Pi*r^2 + 2Pi*r*h
V= h*Pi*r^2
V= (Pi*r^2)[(250-Pi*r^2)/p)
V= 250r - Pi*r^3 / 2

Last one catches my eye. But why, and how ...

- Steve

13. ## Re: Stupid Math ...

Surface Area of a Cylinder = 2 pi r^2 + s r h
Surface Area = Areas of top and bottom +Area of the side

Surface Area = 2(Area of top) + (perimeter of top)* height
Surface Area = 2(pi r^2) + (2 pi r)* h

250 = (pi*r^2) + [(2pi*r)*h]
Isolate for ‘h’
h = [(250-pi*r^2)/(2pi*r)]

V=Pi*r*h
V = pi*r * [(250-pi*r^2)/(2pi*r)]

There… ass….

14. ## Re: Stupid Math ...

Uhm...

I'm going to go grab a soda and then come back to this one. I think I need some caffeine if I'm going to understand this.

15. ## Re: Stupid Math ...

I took off the top in my calculations... hence me not multiplying by 2... ***.. :p there is a bottom to the cylinder.

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