MathDB
AMC 8 2005 Problem 21

Source:

July 23, 2011
geometrygeometric transformationreflectiondilation

Problem Statement

How many distinct triangles can be drawn using three of the dots below as vertices?
[asy]dot(origin^^(1,0)^^(2,0)^^(0,1)^^(1,1)^^(2,1));[/asy]
<spanclass=latexbold>(A)</span> 9<spanclass=latexbold>(B)</span> 12<spanclass=latexbold>(C)</span> 18<spanclass=latexbold>(D)</span> 20<spanclass=latexbold>(E)</span> 24 <span class='latex-bold'>(A)</span>\ 9\qquad<span class='latex-bold'>(B)</span>\ 12\qquad<span class='latex-bold'>(C)</span>\ 18\qquad<span class='latex-bold'>(D)</span>\ 20\qquad<span class='latex-bold'>(E)</span>\ 24