1962 AMC 12 Problem 20
Attempt Problem 20 of the 1962 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1962 AMC 12 solutions, or check the answer key.
All problems are used with official legal permission of the Mathematical Association of America (MAA).
20.
The angles of a pentagon are in arithmetic progression. One of the angles, in degrees, must be:
Answer: A
Small hint:
Five terms in arithmetic progression have their middle term equal to their average
Big hint:
The interior angles of a pentagon sum to
Solution:
The average of the five angles is For five terms in arithmetic progression, the middle term equals the average, so one angle must be
Thus, the correct answer is A.
Problem 20 in other years
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