document.write( "Question 187616: jasmine drew a rectangle which is 143sqare mm. ethan drew a rectangle inside of jasmine's which is 35 square mm. ethan's rectangle has a 3 mm border between his and jasmine's rectangle. what are the length and width of jasmines rectangle?\r
\n" ); document.write( "\n" ); document.write( "after many attempts i believe the answer is 13mm X 11 mm. i have worked backwards but cannot seem to find the equation to use for finding either the length or width. using A = l x w
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Algebra.Com's Answer #140647 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Let x=length of outer rectangle, y=width of outer rectangle\r
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\n" ); document.write( "\n" ); document.write( "If we draw a picture, we get\r
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\n" ); document.write( "\n" ); document.write( "Note: the inner rectangle's dimensions are 6 units less than the corresponding on the outer rectangle since there are two 3 unit lengths per side.\r
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\n" ); document.write( "\n" ); document.write( "Let's set up the equation for the area of the outer rectangle:\r
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\n" ); document.write( "\n" ); document.write( "\"A=LW\" Start with the area of a rectangle formula\r
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\n" ); document.write( "\n" ); document.write( "\"143=xy\" Plug in \"A=143\" (the area of the outer rectangle), \"L=x\", and \"W=y\" (the dimensions of the outer rectangle)\r
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\n" ); document.write( "\n" ); document.write( "\"143%2Fx=y\" Divide both sides by \"x\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=143%2Fx\" Rearrange the equation\r
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\n" ); document.write( "\n" ); document.write( "Now let's set up the equation for the area of the inner rectangle:\r
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\n" ); document.write( "\n" ); document.write( "\"A=LW\" Go back to the area of a rectangle formula\r
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\n" ); document.write( "\n" ); document.write( "\"35=%28x-6%29%28y-6%29\" Plug in \"A=35\" (the area of the inner rectangle), \"L=x-6\", and \"W=y-6\" (the dimensions of the inner rectangle)\r
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\n" ); document.write( "\n" ); document.write( "\"35=xy-6x-6y%2B36\" FOIL\r
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\n" ); document.write( "\n" ); document.write( "\"35=x%28143%2Fx%29-6x-6%28143%2Fx%29%2B36\" Plug in \"y=143%2Fx\"\r
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\n" ); document.write( "\n" ); document.write( "\"35=%28143x%29%2Fx-6x-858%2Fx%2B36\" Multiply\r
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\n" ); document.write( "\n" ); document.write( "\"35=%28143cross%28x%29%29%2Fcross%28x%29-6x-858%2Fx%2B36\" Cancel out the common terms.\r
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\n" ); document.write( "\n" ); document.write( "\"35=143-6x-858%2Fx%2B36\" Simplify\r
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\n" ); document.write( "\n" ); document.write( "\"35x=143x-6x%5E2-858%2B36x\" Multiply EVERY term by the LCD \"x\" to clear out the fractions.\r
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\n" ); document.write( "\n" ); document.write( "\"0=143x-6x%5E2-858%2B36x-35x\" Subtract 35x from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"0=-6x%5E2%2B144x-858\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic equation in the form of \"ax%5E2%2Bbx%2Bc\" where \"a=-6\", \"b=144\", and \"c=-858\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for x\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29\" Start with the quadratic formula\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%28144%29+%2B-+sqrt%28+%28144%29%5E2-4%28-6%29%28-858%29+%29%29%2F%282%28-6%29%29\" Plug in \"a=-6\", \"b=144\", and \"c=-858\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B-+sqrt%28+20736-4%28-6%29%28-858%29+%29%29%2F%282%28-6%29%29\" Square \"144\" to get \"20736\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B-+sqrt%28+20736-20592+%29%29%2F%282%28-6%29%29\" Multiply \"4%28-6%29%28-858%29\" to get \"20592\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B-+sqrt%28+144+%29%29%2F%282%28-6%29%29\" Subtract \"20592\" from \"20736\" to get \"144\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B-+sqrt%28+144+%29%29%2F%28-12%29\" Multiply \"2\" and \"-6\" to get \"-12\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B-+12%29%2F%28-12%29\" Take the square root of \"144\" to get \"12\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-144+%2B+12%29%2F%28-12%29\" or \"x+=+%28-144+-+12%29%2F%28-12%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-132%29%2F%28-12%29\" or \"x+=++%28-156%29%2F%28-12%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+11\" or \"x+=+13\" Reduce \r
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\n" ); document.write( "\n" ); document.write( "So the answers are \"x+=+11\" or \"x+=+13\"\r
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\n" ); document.write( "\n" ); document.write( "This means that the lengths are 11 mm or 13 mm\r
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\n" ); document.write( "\n" ); document.write( "Since the \"length\" is usually the longer of the two measurements, let's make the length 13 mm (it doesn't matter either way).\r
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\n" ); document.write( "\n" ); document.write( "So the width would then be...\r
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\n" ); document.write( "\n" ); document.write( "\"y=143%2Fx\" Go back to the first isolated equation\r
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\n" ); document.write( "\n" ); document.write( "\"y=143%2F13\" Plug in \"x=13\"\r
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\n" ); document.write( "\n" ); document.write( "\"y=11\" Divide\r
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\n" ); document.write( "\n" ); document.write( "So the width is 11 mm (note: this is the other answer)\r
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\n" ); document.write( "\n" ); document.write( "Now subtract 6 mm from each dimension to get\r
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\n" ); document.write( "\n" ); document.write( "13-6=7 and 11-6=5\r
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\n" ); document.write( "\n" ); document.write( "So the inner rectangle's dimensions is 7 mm by 5 mm\r
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\n" ); document.write( "\n" ); document.write( "Answer: \r
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\n" ); document.write( "\n" ); document.write( "So we just found the following...\r
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\n" ); document.write( "\n" ); document.write( "Outer Rectangle: \r
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\n" ); document.write( "\n" ); document.write( "Length = 13 mm, Width = 11 mm\r
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\n" ); document.write( "\n" ); document.write( "Inner Rectangle: \r
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\n" ); document.write( "\n" ); document.write( "Length = 7 mm, Width = 5 mm\r
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\n" ); document.write( "\n" ); document.write( "Check:\r
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\n" ); document.write( "\n" ); document.write( "143=13*11
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\n" ); document.write( "\n" ); document.write( "35=7*5
\n" ); document.write( "35=35...works\r
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