document.write( "Question 858725: This is a calculus problem. A cylindrical container is to hold 20π cm3. The bottom is made of a material that costs $0.80 per cm2, and the top is left open (no material needed). The material for the curved side costs $0.32 per cm2.
\n" ); document.write( " Find the height in centimeters of the most economical container.
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Algebra.Com's Answer #517365 by Fombitz(32388)\"\" \"About 
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Find the volume of a cylinder, \"V=pi%2AR%5E2%2AH=20%2Api\"
\n" ); document.write( "\"R%5E2%2AH=20\"
\n" ); document.write( "Find the total cost by calculating the area of the bottom and area of the side wall and multiplying by cost per unit area.
\n" ); document.write( "\"T=pi%2AR%5E2%280.80%29%2B2%2Api%2AR%2AH%2A%280.32%29\"
\n" ); document.write( "\"T=0.80%2Api%2AR%5E2%2B0.64%2Api%2AR%2AH\"
\n" ); document.write( "From the volume equation, you can find a relationship between H and R.
\n" ); document.write( "\"H=20%2FR%5E2\"
\n" ); document.write( "Substitute,
\n" ); document.write( "\"T=0.80%2Api%2AR%5E2%2B0.64%2Api%2AR%2A%2820%2FR%5E2%29\"
\n" ); document.write( "\"T=0.80%2Api%2AR%5E2%2B%2812.8%2Api%29%2AR%5E%28-1%29\"
\n" ); document.write( "Now you have total cost T as a function of one variable.
\n" ); document.write( "Take the derivative and set it to zero.
\n" ); document.write( "\"dT%2FdR=1.60%2Api%2AR-12.8%2Api%2AR%5E%28-2%29\"
\n" ); document.write( "\"1.60%2Api%2AR-12.8%2Api%2AR%5E%28-2%29=0\"
\n" ); document.write( "\"1.6%2AR=12.8.R%5E2\"
\n" ); document.write( "\"R%5E3=12.8%2F1.6\"
\n" ); document.write( "\"R%5E3=8\"
\n" ); document.write( "\"R=2\"
\n" ); document.write( "Then,
\n" ); document.write( "\"H=20%2F%282%5E2%29=5\"
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\n" ); document.write( "\"T=0.80%2Api%2A4%2B0.64%2Api%2A2%2A5\"
\n" ); document.write( "\"T=10.053%2B20.106\"
\n" ); document.write( "\"T=30.16\"\r
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