document.write( "Question 1099943: A box is constructed out of two different types of metal. The metal for the top and bottom, which are both square, costs $5 per square foot and the metal for the sides costs $2 per square foot. Find the dimensions that minimize cost if the box has a volume of 15 cubic feet. \n" ); document.write( "
Algebra.Com's Answer #714545 by ankor@dixie-net.com(22740)\"\" \"About 
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A box is constructed out of two different types of metal.
\n" ); document.write( " The metal for the top and bottom, which are both square, costs $5 per square foot and the metal for the sides costs $2 per square foot.
\n" ); document.write( " Find the dimensions that minimize cost if the box has a volume of 15 cubic feet.
\n" ); document.write( ":
\n" ); document.write( "let s = one side of the square base
\n" ); document.write( "let h = the height of the box
\n" ); document.write( "then
\n" ); document.write( "s^2 * h = 15 cu/ft
\n" ); document.write( "Therefore
\n" ); document.write( "h = \"15%2Fs%5E2\"
\n" ); document.write( ":
\n" ); document.write( "surface area = top, bottom, 4 side areas
\n" ); document.write( "SA = 2s^2 + 4hs
\n" ); document.write( "replace h with \"15%2Fs%5E2\"
\n" ); document.write( "SA = 2s^2 + 4s*\"15%2Fs%5E2\"
\n" ); document.write( "cancel the s
\n" ); document.write( "SA = 2s^2 + (60/s)
\n" ); document.write( "Cost of the box
\n" ); document.write( "C(x) = 5(2x^2) + 2(60/s)
\n" ); document.write( "C(x) = 10x^2 + \"120%2Fs\"
\n" ); document.write( ":
\n" ); document.write( "Graphically, y axis = the cost
\n" ); document.write( "\"+graph%28+300%2C+200%2C+-3%2C+5%2C+-20%2C+160%2C+10x%5E2%2B%28120%2Fx%29%2C+99.26%29+\"
\n" ); document.write( "minimum cost when x=1.9 ft
\n" ); document.write( "find the height
\n" ); document.write( "h = \"15%2F1.9%5E2\"
\n" ); document.write( "h = 4.155 ft
\n" ); document.write( ":
\n" ); document.write( "The dimensions for minimum cost: 1.9 by 1.9 by 4.155 ft Cost about $99.26 (green)
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