document.write( "Question 1111119: ABCD is a square with side length x cm. M and N are the midpoints of AD and CD respectively. The midpoints and point B make a triangle which is the shaded area. Find the ratio of the shaded to unshaded area. \n" ); document.write( "
Algebra.Com's Answer #726202 by KMST(5328)\"\" \"About 
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THE PICTURE:
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\n" ); document.write( "THE FIFTH_GRADER'S SOLUTION:
\n" ); document.write( "If we connect M to the midpoint of BC,
\n" ); document.write( "and N to the midpoint of AB, we split the square into 4 smaller squares, each one being \"1%2F4\" of square ABCD.
\n" ); document.write( "Joining 2 of those small squares we would get a rectangle
\n" ); document.write( "that is \"1%2F2\" of square ABCD.
\n" ); document.write( "One of those 4 smaller squares
\n" ); document.write( "is divided into two equal triangular parts by diagonal MN,
\n" ); document.write( "so each of those two triangles is \"1%2F8\" of square ABCD.
\n" ); document.write( "Triangle MND is \"1%2F8\" of square ABCD.
\n" ); document.write( "
\n" ); document.write( "The diagonal of a rectangle that is \"1%2F4%2B1%2F4=1%2F2\" of square ABCD
\n" ); document.write( "(such as diagonal MB),
\n" ); document.write( "divides the rectangle into two equal triangles.
\n" ); document.write( "Each of those triangles is \"1%2F4\" of square ABCD.
\n" ); document.write( "Triangle ABM is \"1%2F4\" of square ABCD, and so is triangle NCB.\r
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\n" ); document.write( "The unshaded area is triangles ABM + NCB + MND, and amounts to
\n" ); document.write( "\"1%2F4%2B1%2F4%2B1%2F8=5%2F8\" of the square.
\n" ); document.write( "So, the shaded area is
\n" ); document.write( "\"1-5%2F8=3%2F8\" of the square.
\n" ); document.write( "Obviously the ratio of shaded area to unshaded area is
\n" ); document.write( "\"3%2F8\"\"%22%3A%22\"\"5%2F8\" or \"3%3A5\"
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\n" ); document.write( "THE EXPECTED SOLUTION is probably as follows
\n" ); document.write( "As ABCD is a square with side length \"x\" cm\",
\n" ); document.write( "\"AB=BC=CD=AD=x\"\"cm\" .
\n" ); document.write( "As \"M and N are the midpoints of AD and CD respectively\",
\n" ); document.write( "\"AM=MD=DN=NC=x%2F2\"\"cm\" .
\n" ); document.write( "The unshaded area is made up of triangles \"ABM\" , \"NCB\" , and \"MND\" ,
\n" ); document.write( "so its total area is easy to calculate.
\n" ); document.write( "\"area%28ABM%29\"\"%22=%22\"\"%281%2F2%29%2AAB%2AAM\"\"%22=%22\"\"%281%2F2%29%2A%22%28+x%22\"\"%22cm+%29%22\"\"%22+%22%2A%22+%22\"\"%22%28%22\"\"x%2F2\"\"%22cm+%29%22\"\"%22=%22\"\"x%5E2%2F4\"\"cm%5E2\" .
\n" ); document.write( "\"area%28NCB%29\"\"%22=%22\"\"%281%2F2%29%2ACB%2ANC\"\"%22=%22\"\"%281%2F2%29%2A%22%28+x%22\"\"%22cm+%29%22\"\"%22+%22%2A%22+%22\"\"%22%28%22\"\"x%2F2\"\"%22cm+%29%22\"\"%22=%22\"\"x%5E2%2F4\"\"cm%5E2\" .
\n" ); document.write( "\"area%28MND%29\"\"%22=%22\"\"%281%2F2%29%2AMD%2AND\"\"%22=%22\"\"%281%2F2%29%2A%22%28%22\"\"x%2F2\"\"%22cm+%29%22\"\"%22+%22%2A%22+%22\"\"%22%28%22\"\"x%2F2\"\"%22cm+%29%22\"\"%22=%22\"\"x%5E2%2F8\"\"cm%5E2\" .
\n" ); document.write( "\"unshaded\"\"area\"\"%22=%22\"\"%28x%5E2%2F4%2Bx%5E2%2F4%2Bx%5E2%2F8%29\"\"cm%5E2\"\"%22=%22\"\"%285%2F8%29x%5E2\"\"cm%5E2\"
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\n" ); document.write( "Calculating the shaded area as the area of triangle MNB may seem difficult,
\n" ); document.write( "However,
\n" ); document.write( "\"area%28MNB%29\"\"%22=%22\"\"shaded\"\"area\"\"%22=%22\"\"area%28ABCD%29\"\"%22-%22\"\"unshaded\"\"area\"
\n" ); document.write( "\"area%28ABCD%29\"\"%22=%22\"\"AB%2ABC\"\"%22=%22\"\"%22%28+x%22\"\"%22cm+%29%22%5E2\"\"%22=%22\"\"x%5E2\"\"cm%5E2\"
\n" ); document.write( "So, \"area%28MNB%29\"\"%22=%22\"\"shaded\"\"area\"\"%22=%22\"\"x%5E2\"\"cm%5E2\"\"%22-%22\"\"%285%2F8%29x%5E2\"\"cm%5E2\"\"%22=%22\"\"%283%2F8%29x%5E2\"\"cm%5E2\" .
\n" ); document.write( "The ratio of those two area values, both in \"cm%5E2\" is
\n" ); document.write( "\"%28%283%2F8%29%29%2F%28%285%2F8%29%29\"\"%22=%22\"\"%283%2F8%29%2A%288%2F5%29\"\"%22=%22\"\"highlight%283%2F5%29\" or \"highlight%283%3A5%29\"
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