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20

Part of 2004 AMC 10

Problems(2)

Problem: 2004 AMC 10 #20

Source:

2/1/2007
Points EE and FF are located on square ABCDABCD so that ΔBEF\Delta BEF is equilateral. What is the ratio of the area of ΔDEF\Delta DEF to that of ΔABE\Delta ABE?
[asy] pair A=origin, B=(1,0), C=(1,1), D=(0,1), X=B+2*dir(165), E=intersectionpoint(B--X, A--D), Y=B+2*dir(105), F=intersectionpoint(B--Y, D--C); draw(B--C--D--A--B--F--E--B); pair point=(0.5,0.5); label("AA", A, dir(point--A)); label("BB", B, dir(point--B)); label("CC", C, dir(point--C)); label("DD", D, dir(point--D)); label("EE", E, dir(point--E)); label("FF", F, dir(point--F));[/asy]
<spanclass=latexbold>(A)</span>  43<spanclass=latexbold>(B)</span>  32<spanclass=latexbold>(C)</span>  3<spanclass=latexbold>(D)</span>  2<spanclass=latexbold>(E)</span>  1+3<span class='latex-bold'>(A)</span>\; \frac43\qquad <span class='latex-bold'>(B)</span>\; \frac32\qquad <span class='latex-bold'>(C)</span>\; \sqrt3\qquad <span class='latex-bold'>(D)</span>\; 2\qquad <span class='latex-bold'>(E)</span>\; 1+\sqrt3\qquad
ratiogeometry
Intersecting Lines in a Triangle

Source:

1/15/2009
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}
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