document.write( "Question 834980: how many triangles can be obtained by joining 12 points, five of which are collinear ? \n" ); document.write( "
Algebra.Com's Answer #503272 by Edwin McCravy(20055)\"\" \"About 
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document.write( "[We assume that no three of the other 7 points are collinear.]\r\n" );
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document.write( "If no three of the 12 points were collinear the answer would \r\n" );
document.write( "be C(12,3)=220 triangles.  But for every choice of three \r\n" );
document.write( "collinear points, we lose one triangle. There are C(5,3)=10 \r\n" );
document.write( "choices of three collinear points, so we lose C(5,3)=10 \r\n" );
document.write( "triangles.\r\n" );
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document.write( "Answer:  C(12,3) - C(5,3) = 220 - 10 = 210.\r\n" );
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document.write( "Edwin
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