document.write( "Question 882262: Trying to help my son figure out surface area of a cylinder.
\n" ); document.write( "What is the surface area if the radius is 4 ft. and the height is 21 ft.
\n" ); document.write( "Do you do as follows:
\n" ); document.write( "2(3.14)(8)+ 2(3.14)(4)(21) = 577.76.
\n" ); document.write( "Not sure that is correct. Where are we going wrong?
\n" ); document.write( "Tx for your help!!!! Final tomorrow :) \n" ); document.write( "

Algebra.Com's Answer #532749 by josgarithmetic(39617) $\"\"$ $\"About$

You can put this solution on YOUR website!
Not sure what level since you did not say.\r
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\n" ); document.write( "\n" ); document.write( "Cutting the open cylinder along its length and unroll, you find the unrolled length corresponds to the circumference of the rolled form; and the length along which the cylinder was cut is \"height\" of this unrolled form. You also have the two disc surfaces.\r
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\n" ); document.write( "\n" ); document.write( "You have then two terms to be added for the total surface area:
\n" ); document.write( " $\"h%2A%282pi%2Ar%29%2B2%28pi%2Ar%5E2%29\"$ , the sum of the unrollable curved tube and the two circular discs. You know h=21, and r=4, so you can replace the variables with them.\r
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\n" ); document.write( "\n" ); document.write( "We have Commutative Property of Addition, so you can also say $\"2%28pi%2Ar%5E2%29%2Bh%282pi%2Ar%29\"$ . \n" ); document.write( "

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