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2003 AMC 10A Problem 7

Problem 7 of 25EasierGeometryProblem-Solving Techniques

How many non-congruent triangles with perimeter 77 have integer side lengths?

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Solution

The longest side cannot exceed 3,3, since otherwise the other two sides could not reach it. The only possibilities are side lengths 1,1, 3,3, 33 and 2,2, 2,2, 3,3, giving 22 triangles. Thus, the correct answer is B.
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Tagged: triangle inequality · systematic listing

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