2014 AMC 12B Problems/Problem 12
Problem
A set S consists of triangles whose sides have integer lengths less than 5, and no two elements of S are congruent or similar. What is the largest number of elements that S can have?
$\textbf{(A)}\ 8\qquad\textbf{(B)}\ 9\qquad\textbf{(C)}\ 10\qquad\textbf{(D)}}\ 11\qquad\textbf{(E)}\ 12$ (Error compiling LaTeX. Unknown error_msg)
Solution
Define to be the set of all triples such that , , and . Now we enumerate the elements of :
It should be clear that is simply minus the larger "duplicates" (e.g. is a larger duplicate of ). Since is and the number of higher duplicates is , the answer is or .