MathDB
Intersecting Lines in a Triangle

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January 15, 2009
ratioLaTeXanalytic geometryAoPSwikigeometryAMCAIME

Problem Statement

In ABC \triangle ABC points D D and E E lie on BC \overline{BC} and AC \overline{AC}, respectively. If AD \overline{AD} and BE \overline{BE} intersect at T T so that AT/DT \equal{} 3 and BT/ET \equal{} 4, what is CD/BD CD/BD? [asy]unitsize(2cm); defaultpen(linewidth(.8pt));
pair A = (0,0); pair C = (2,0); pair B = dir(57.5)*2; pair E = waypoint(C--A,0.25); pair D = waypoint(C--B,0.25); pair T = intersectionpoint(D--A,E--B);
label("BB",B,NW);label("AA",A,SW);label("CC",C,SE);label("DD",D,NE);label("EE",E,S);label("TT",T,2*W+N);
draw(A--B--C--cycle); draw(A--D); draw(B--E);[/asy]<spanclass=latexbold>(A)</span> 18<spanclass=latexbold>(B)</span> 29<spanclass=latexbold>(C)</span> 310<spanclass=latexbold>(D)</span> 411<spanclass=latexbold>(E)</span> 512 <span class='latex-bold'>(A)</span>\ \frac {1}{8}\qquad <span class='latex-bold'>(B)</span>\ \frac {2}{9}\qquad <span class='latex-bold'>(C)</span>\ \frac {3}{10}\qquad <span class='latex-bold'>(D)</span>\ \frac {4}{11}\qquad <span class='latex-bold'>(E)</span>\ \frac {5}{12}