MathDB
3-4-5 triangle; find length of segment

Source: AMC 10 2011 b Problem 9

February 24, 2011
geometryratioAMC

Problem Statement

The area of EBD\triangle EBD is one third of the area of 3453-4-5 ABC \triangle ABC. Segment DEDE is perpendicular to segment ABAB. What is BDBD?
[asy] unitsize(10mm); defaultpen(linewidth(.8pt)+fontsize(10pt)); dotfactor=4; pair A=(0,0), B=(5,0), C=(1.8,2.4), D=(5-4sqrt(3)/3,0), E=(5-4sqrt(3)/3,sqrt(3)); pair[] ps={A,B,C,D,E}; draw(A--B--C--cycle); draw(E--D); draw(rightanglemark(E,D,B)); dot(ps); label("AA",A,SW); label("BB",B,SE); label("CC",C,N); label("DD",D,S); label("EE",E,NE); label("33",midpoint(A--C),NW); label("44",midpoint(C--B),NE); label("55",midpoint(A--B),SW);[/asy]
<spanclass=latexbold>(A)</span> 43<spanclass=latexbold>(B)</span> 5<spanclass=latexbold>(C)</span> 94<spanclass=latexbold>(D)</span> 433<spanclass=latexbold>(E)</span> 52 <span class='latex-bold'>(A)</span>\ \frac{4}{3} \qquad <span class='latex-bold'>(B)</span>\ \sqrt{5} \qquad <span class='latex-bold'>(C)</span>\ \frac{9}{4} \qquad <span class='latex-bold'>(D)</span>\ \frac{4\sqrt{3}}{3} \qquad <span class='latex-bold'>(E)</span>\ \frac{5}{2}