document.write( "Question 1100341: A roll of news paper of length 7000m and thickness 0.022cm is rolled into a solid cylinder. Then it's radius is what? \n" ); document.write( "

Algebra.Com's Answer #714859 by greenestamps(13200) $\"\"$ $\"About$

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Let x be the width in meters of the roll of newspaper.

\n" ); document.write( "We need to use consistent units; so call the thickness of the newspaper 0.00022m.

\n" ); document.write( "Spread out into a rectangular sheet, the newspaper is a very thin rectangular solid with length 7000, width x, and thickness 0.00022. The volume is then 1.54x cubic meters.

\n" ); document.write( "When rolled into a cylinder, the volume will be the same.

\n" ); document.write( "The volume of a cylinder is (pi)*(radius squared)*(height); the height of the cylinder is the width of the newspaper. So

\n" ); document.write( " $\"1.54x+=+%28pi%29%28r%5E2%29x\"$
\n" ); document.write( " $\"r%5E2+=+1.54%2F%28pi%29+=+0.49\"$ (approximately... 0.490197....)
\n" ); document.write( " $\"r+=+sqrt%280.49%29+=+0.7\"$

\n" ); document.write( "The radius of the roll of newspaper is approximately 0.7m. \n" ); document.write( "

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