Question 1197026
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How many feet of piping can be made from 5 cubic feet of iron 
if the outer and inner diameters of the pipe are 8 and 6 inches, respectively?
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            The solution by @josgarithmetic is  INCORRECT,  as usual.


            I came to bring a correct solution.



<pre>
Outer diameter is 8 inches = {{{2/3}}} ft;  inner diameter is 6 inches = {{{1/2}}} ft.

Outer radius is  {{{1/3}}} ft;  inner radius is  {{{1/4}}} ft.


The cross-section area is  A = {{{pi*(1/3)^2}}} - {{{pi*(1/4)^2}}} = {{{pi*(1/9-1/16)}}} = {{{pi*((16-9)/(9*16))}}} = {{{pi*(7/144)}}} square feet.


For the pipe length L we have this equation

    A*L = 5 cubic feet,  or  {{{pi*(7/144)*L}}} = 5.


From this equation

    L = {{{5/(pi*(7/144))}}} = {{{(5*144)/(3.14159*7)}}} = 32.74 ft  (rounded).   


<U>ANSWER</U>.  The pipe length is about 32.74 ft.
</pre>

Solved.


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Formula in the post by @josgarithmetic is &nbsp;INCORRECT - - - even do not try to use it.


For your safety, &nbsp;you better ignore his post.



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He re-wrote everything from me after seeing my post.