document.write( "Question 93440: A garden area is 30ft. long and 20ft. wide. A path of uniform width is set around the edge. If the remaining garden is 400ft.^2, what is the width of the path? \n" ); document.write( "
Algebra.Com's Answer #68030 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
If we draw a picture we get\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "If we let x be the width of the path, notice there are 2 x-values per side. So we add 2x to 20 to get 20+2x. This is the total length of the side that contains 20 feet. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Also, this means we add 2x to 30 to get 30+2x. This is the total length of the side that contains 30 feet. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So that means the total area can be written as:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"A=%2820%2B2x%29%2830%2B2x%29\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now lets find the inner area:\r
\n" ); document.write( "\n" ); document.write( "\"A=20%2A30=600\" plug in the garden dimensions\r
\n" ); document.write( "\n" ); document.write( "So the inner area is 600 sq ft\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now lets find the total area\r
\n" ); document.write( "\n" ); document.write( "inner area+remaining area=600+400=1000\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the total area is 1000 sq ft\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=%2820%2B2x%29%2830%2B2x%29\" Plug in \"A=1000\" (this is the total area)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=600%2B100x%2B4x%5E2\" Foil\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"0=600%2B100x%2B4x%5E2-1000\" Subtract 1000 from both sides\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"0=4x%5E2%2B100x-400\" Combine like terms\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for x:\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Starting with the general quadratic\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"ax%5E2%2Bbx%2Bc=0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "the general solution using the quadratic equation is:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So lets solve \"4%2Ax%5E2%2B100%2Ax-400=0\" ( notice \"a=4\", \"b=100\", and \"c=-400\")\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+sqrt%28+%28100%29%5E2-4%2A4%2A-400+%29%29%2F%282%2A4%29\" Plug in a=4, b=100, and c=-400\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+sqrt%28+10000-4%2A4%2A-400+%29%29%2F%282%2A4%29\" Square 100 to get 10000 \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+sqrt%28+10000%2B6400+%29%29%2F%282%2A4%29\" Multiply \"-4%2A-400%2A4\" to get \"6400\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+sqrt%28+16400+%29%29%2F%282%2A4%29\" Combine like terms in the radicand (everything under the square root)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+20%2Asqrt%2841%29%29%2F%282%2A4%29\" Simplify the square root (note: If you need help with simplifying the square root, check out this solver)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B-+20%2Asqrt%2841%29%29%2F8\" Multiply 2 and 4 to get 8\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So now the expression breaks down into two parts\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-100+%2B+20%2Asqrt%2841%29%29%2F8\" or \"x+=+%28-100+-+20%2Asqrt%2841%29%29%2F8\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now break up the fraction\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=-100%2F8%2B20%2Asqrt%2841%29%2F8\" or \"x=-100%2F8-20%2Asqrt%2841%29%2F8\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Simplify\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=-25+%2F+2%2B5%2Asqrt%2841%29%2F2\" or \"x=-25+%2F+2-5%2Asqrt%2841%29%2F2\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So these expressions approximate to\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=3.50781059358212\" or \"x=-28.5078105935821\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So our possible solutions are:\r
\n" ); document.write( "\n" ); document.write( "\"x=3.50781059358212\" or \"x=-28.5078105935821\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Since a negative length doesn't make sense, our only solution is \"x=3.50781059358212\" which is 3.507 to the nearest thousandth\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "-----------------------------\r
\n" ); document.write( "\n" ); document.write( "Check:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=%2820%2B2x%29%2830%2B2x%29\" Start with the given area function\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=%2820%2B2%283.508%29%29%2830%2B2%283.507%29%29\" plug in x=3.507\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=%2820%2B7.016%29%2830%2B7.014%29\" multiply\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=%2827.016%29%2837.014%29\" Add\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"1000=999.970224\" Since we rounded, this is as close as it gets. So our answer is verified.
\n" ); document.write( "
\n" );