Maths Olympiad Prep

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Geometry Difficulty 3.2 AMC 10/12 Find the answer

How many non-similar triangles have angles whose degree measures are distinct positive integers in arithmetic progression?

Pick one

Solution

The sum of the angles of a triangle is 180180 degrees. For an arithmetic progression with an odd number of terms, the middle term is equal to the average of the sum of all of the terms, making it 1803=60\frac{180}{3} = 60 degrees. The minimum possible value for the smallest angle is 11 and the highest possible is 5959 (since the numbers are distinct), so there are (C) 59\boxed{\textbf{(C) }59} possibilities.

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.