document.write( "Question 1012461: A piece of wire 6 metres long is cut into 2 parts. One part is used to form a square and the other to make a rectangle whose length is 3 times its breadth. Find the lengths of the 2 parts if the sum of the two areas is a minimum. \n" ); document.write( "
Algebra.Com's Answer #628414 by ankor@dixie-net.com(22740)![]() ![]() You can put this solution on YOUR website! A piece of wire 6 metres long is cut into 2 parts. \n" ); document.write( " One part is used to form a square and the other to make a rectangle whose length is 3 times its breadth. \n" ); document.write( " Find the lengths of the 2 parts if the sum of the two areas is a minimum. \n" ); document.write( ": \n" ); document.write( "let s = the side of the square \n" ); document.write( "let L = the length of the rectangle \n" ); document.write( "let W = the width \n" ); document.write( "therefore the two perimeters = 6 \n" ); document.write( "4s + 2L + 2W = 6 \n" ); document.write( "Simplify, divide equation by 2 \n" ); document.write( "2s + L + W = 3 \n" ); document.write( "Given that \n" ); document.write( "L = 3W \n" ); document.write( "therefore \n" ); document.write( "2s + 3W + W = 3 \n" ); document.write( "2s + 4W = 3: \n" ); document.write( "Simplify, divide by 2 \n" ); document.write( "s + 2W = 1.5 \n" ); document.write( "s = -2W+1.5 \n" ); document.write( ": \n" ); document.write( "the total area \n" ); document.write( "A = s^2 + LW \n" ); document.write( "Replace s with (-2W+1.5), replace L with 3W \n" ); document.write( "A = (-2W+1.5)^2 + 3W(W) \n" ); document.write( "FOIL \n" ); document.write( "A = 4W^2 - 3W - 3W + 2.25 + 3W^2 \n" ); document.write( "Combine like terms \n" ); document.write( "A = 7W^2 - 6W + 2.25 \n" ); document.write( "Find the minimum by finding the axis of symmetry, x=-b/(2a) \n" ); document.write( "w = \n" ); document.write( "W = \n" ); document.write( "W = .42857 is the width for minimum area \n" ); document.write( "Find L \n" ); document.write( "3(.42857) = 1.2857 is the length \n" ); document.write( "Find the length of the portion made into a rectangle (perimeter) \n" ); document.write( "P = 2(1.2857 + 2(.42857) \n" ); document.write( "P = 3.42856m is the portion made into a rectangle \n" ); document.write( "then \n" ); document.write( " 6 - 3.42856 = 2.57m is the portion made into a square \n" ); document.write( ": \n" ); document.write( ": \n" ); document.write( " \n" ); document.write( " |