Question 200166
A rectangular piece of sheet metal with an area of 800 in^2 is to be bent
 into a cylindrical length of stovepipe having a volume of 400 in^3.
 What are the dimensions of the sheet metal? 
:
Label the rectangular piece of metal as follows:
;
Let h = the length, (will be the length of the pipe)
Let c = the width, (will be the circumference of the pipe
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The area of the metal
h * c = 800
h = {{{800/c}}}
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Find the radius from the circumference
2*pi*r = c
r = {{{c/(2pi)}}}
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The volume:
pi*r^2*h = 400
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Substitute (c/2pi) for r, and (800/c) for h
pi*{{{c/(2pi)}}}*{{{c/(2pi)}}}*{{{800/c)}}} = 400
cancel out a pi and a c
{{{c/2}}}*{{{1/(2pi)}}}*800 = 400
:
{{{c/(4pi)}}}*800 = 400
Cancel the 4 into 800
{{{(200c)/pi}}} = 400
:
200c = 400*pi
;
divide 200 into both sides
c = 2*pi
:
c = 6.283 is the circumference of the pipe
;
Find the height
h = {{{800/c}}}
h = {{{800/6.283}}}
h = 127.33" is the height of the pipe
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The dimensions of the metal: 127.33" by 6.283"
:
:
Check solution by finding the volume with these value
Find r
r = {{{c/(2pi)}}}
r = {{{6.283/(2pi)}}}
r = 1"
:
V = pi*1^2*127.33
V = 400.0 cu/in