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Help! Total mental block

Don't you hate it when theres just one part of the problem that you just cannot get? And lucky me it's part a, which of course you need for the rest of the problem :stupido2:

A parcel is to be tied with a length of string (see my lovely artistic diagram courtesy of paint) Assume the parcel is a cuboid with a square cross section and a fixed volume. Find an expression for the length of string

http://img.photobucket.com/albums/v473/Twunkie/maths.jpg


Well any help would be appreciated because i just can't think of how to do this without being told the volume.
4x + 4y ?
Reply 2
Avatar for SaraTwix
SaraTwix
OP
tried that, I need to express it in terms of only one variable as i need to differentiate after I have my equation, find dimensions etc etc
Reply 3
Avatar for SsEe
SsEe
13
Call the volume v. It's just an unknown constant.
v = x²y
l = 4x + 4y = 4x + 4v/(x²)
Reply 4
Avatar for SaraTwix
SaraTwix
OP
Well that makes sense but i don't really understand how I could use that equation to find the dimensions of the box? One of the questions is to find the minimum length of string which I know how to do by differentiating
I' = 4 - 8v/(x^3) ? but I'm not quite sure what i'm supposed to be doing with V, or if i'm thinking completly back to front.

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