Question 1205007
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A tight roll of paper as delivered to the printer is 60cm in diameter and the paper 
is wound onto a wooden cylinder 8cm in diameter. The paper is 0.005 cm thick. 
What length of paper is there in the roll in km?
(Hint: Compare the area of the edge of the paper when rolled with that of the paper when unrolled)
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<pre>
The given parameters are:

    Inner diameter {{{d[1]}}} =  8 cm

    Outer diameter {{{d[2]}}} = 60 cm 


The area between the two circles is

    Area = {{{(pi*d[2]^2)/4}}} - {{{(pi*d[1]^2)/4}}} = {{{3.14159265*((60/2)^2-(8/2)^2)}}} = 2777.167903 cm^2.


The length of the paper is then calculated as:

    Length = {{{Area/0.005}}} centimeters.


This gives

   Length = {{{2777.167903/0.005}}} = 555433.5806 cm,  or  5554.34 meters.  (rounded).  


<U>ANSWER</U>.  The length of the paper in the roll is 5554.34 meters or 5.55434 kilometer (rounded).
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Solved.