document.write( "Question 1102748: The surface area of a right circular cylinder of height 4 feet and radius r feet is given by S(r)=2πrh+2πr2. Find the instantaneous rate of change of the surface area with respect to the radius, r, when r = 4.
\n" ); document.write( "A) 24π
\n" ); document.write( "B) 16π
\n" ); document.write( "C) 64π
\n" ); document.write( "D) 20π \n" ); document.write( "

Algebra.Com's Answer #717495 by Fombitz(32388) $\"\"$ $\"About$

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Take the derivative of the surface area function with respect to r,
\n" ); document.write( " $\"dS%2Fdr=2pi%2Ah%2B4pi%2Ar\"$
\n" ); document.write( " $\"dS%2Fdr=2pi%28h%2B2r%29\"$
\n" ); document.write( "So when $\"r=4\"$ ,
\n" ); document.write( " $\"dS%2Fdr=2pi%284%2B2%284%29%29\"$
\n" ); document.write( "Work that out for the solution.
\n" ); document.write( " \n" ); document.write( "

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