document.write( "Question 218034: Dalton has a closed rectangular box with a square base at least 10 inches long have a surface area of 900 square inches. what dimensions will give the box a maximum volume? \n" ); document.write( "
Algebra.Com's Answer #164363 by ankor@dixie-net.com(22740)\"\" \"About 
You can put this solution on YOUR website!
Dalton has a closed rectangular box with a square base at least 10 inches long
\n" ); document.write( " have a surface area of 900 square inches.
\n" ); document.write( " what dimensions will give the box a maximum volume?
\n" ); document.write( ";
\n" ); document.write( "Let x = the side of the square base
\n" ); document.write( "Actually the maximum is when the box is a perfect cube, therefore
\n" ); document.write( "let x = the height of the box also
\n" ); document.write( ":
\n" ); document.write( "Surface area equation, find h:
\n" ); document.write( "6x^2 = 900
\n" ); document.write( "simplify divide by 6
\n" ); document.write( "x^2 = 150
\n" ); document.write( "x = \"sqrt%28150%29\"
\n" ); document.write( "x = 12.247\"
\n" ); document.write( ":
\n" ); document.write( "Max vol: 12.247 by 12.247 by 12.247, and 12.247^3 = 1836.9 cu/in
\n" ); document.write( ":
\n" ); document.write( "You can prove this:
\n" ); document.write( "let the height = h,
\n" ); document.write( ":
\n" ); document.write( "Surface area equation, find h:
\n" ); document.write( "2x^2 + 4xh = 900
\n" ); document.write( "simplify divide by 2
\n" ); document.write( "x^2 + 2xh = 450
\n" ); document.write( "2xh = -x^2 + 450
\n" ); document.write( "h = \"%28-x%5E2+%2B+450%29%2F%282x%29\"
\n" ); document.write( ":
\n" ); document.write( "Volume equation
\n" ); document.write( "V = x^2 * h
\n" ); document.write( "Replace h
\n" ); document.write( "V = x^2(\"%28-x%5E2+%2B+450%29%2F%282x%29\")
\n" ); document.write( "V = x(\"%28-x%5E2+%2B+450%29%2F2\")
\n" ); document.write( "V = x(\"%28-x%5E3+%2B+450x%29%2F2\")
\n" ); document.write( "
\n" ); document.write( "Graph this equation y=V
\n" ); document.write( "\"+graph%28+300%2C+200%2C+-6%2C+30%2C+-1000%2C+2000%2C+%28-x%5E3%2B450x%29%2F2%29+\"
\n" ); document.write( ":
\n" ); document.write( "Shows max volume when x is a little over 12\"; vol is about 1800 cu/in\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );