Thread: please help very urgent

A box manufacturer is to make a closed box of volume 288 in3, where the base is a rectangle whose length is three times its width. What is the length of the box that uses the least amount of material?

if you make a drawing of your box (a cross + a top)
and if you call h the hight (in inch)
----------------w the width
----------------3*w the length

the surface of the matérial you are using (wich you have to minimized) is
S=2*( (w*3w)+(w*h)+(3*w*h))
and you have got to get h*w*(3*w)=288 inch^3

that may give you a clue!

thanks a lot ....