MathDB
1993 AMC 12 #25 - Rays and a Point

Source:

January 2, 2012
AMC

Problem Statement

Let SS be the set of points on the rays forming the sides of a 120120^{\circ} angle, and let PP be a fixed point inside the angle on the angle bisector. Consider all distinct equilateral triangles PQRPQR with QQ and RR in SS. (Points QQ and RR may be on the same ray, and switching the names of QQ and RR does not create a distinct triangle.) There are [asy] draw((0,0)--(6,10.2), EndArrow); draw((0,0)--(6,-10.2), EndArrow); draw((0,0)--(6,0), dotted); dot((6,0)); label("P", (6,0), S); [/asy] <spanclass=latexbold>(A)</span> exactly 2 such triangles<spanclass=latexbold>(B)</span> exactly 3 such triangles<spanclass=latexbold>(C)</span> exactly 7 such triangles<spanclass=latexbold>(D)</span> exactly 15 such triangles<spanclass=latexbold>(E)</span> more than 15 such triangles <span class='latex-bold'>(A)</span>\ \text{exactly 2 such triangles} \\ \qquad<span class='latex-bold'>(B)</span>\ \text{exactly 3 such triangles} \\ \qquad<span class='latex-bold'>(C)</span>\ \text{exactly 7 such triangles} \\ \qquad<span class='latex-bold'>(D)</span>\ \text{exactly 15 such triangles} \\ \qquad<span class='latex-bold'>(E)</span>\ \text{more than 15 such triangles}