document.write( "Question 1195835: The trapezoid shown is divided into four triangles by its diagonals. The area of two triangles are indicated(9 and 25). What is the area of the whole trapezoid?
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Algebra.Com's Answer #828402 by ikleyn(52847)\"\" \"About 
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document.write( "Let \"a\" be the shorter base of the trapezoid;\r\n" );
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document.write( "let \"b\" be the longer base of the trapezoid.\r\n" );
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document.write( "The triangles of the areas 9 and 25 square units are similar, \r\n" );
document.write( "with the similarity coefficient of \"3%2F5\" (smaller to larger).\r\n" );
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document.write( "Let h be the height of the smaller triangle drawn to its base \"a\";\r\n" );
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document.write( "Let H be the height of the larger triangle drawn to its base \"b\".\r\n" );
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document.write( "Then from the similarity of triangles,  b = \"%285%2F3%29a\";  H = \"%285%2F3%29h\".\r\n" );
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document.write( "We have then  \"%28a%2Bb%29%2F2\" = \"%28a+%2B+%285%2F3%29a%29%2F2\" = \"%288%2F6%29a\" = \"%284%2F3%29a\";\r\n" );
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document.write( "              h + H = \"h+%2B+%285%2F3%29h\" = \"%288%2F3%29h\".\r\n" );
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document.write( "The area of the trapezoid is  \r\n" );
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document.write( "    Area = \"%28%28a%2Bb%29%2F2%29%2A%28h%2BH%29\" = \"%284%2F3%29a%2A%288%2F3%29h\" = \"%2832%2F9%29%2Aah\";\r\n" );
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document.write( "    but  \"%28ah%29%2F2%29\" = the area of the upper triangle = 9;  hence  ah = 2*9;  therefore\r\n" );
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document.write( "    Area = \"%2832%2F9%29%2A%282%2A9%29\" = 32*2 = 64 square units.\r\n" );
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document.write( "ANSWER.  The area of the trapezoid is 64 square units.\r\n" );
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