2022 AMC 12A Problem 25
Attempt Problem 25 of the 2022 AMC 12A 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 2022 AMC 12A solutions, or check the answer key.
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25.
A circle with integer radius is centered at Distinct line segments of length connect points to for and are tangent to the circle, where and are all positive integers and What is the ratio for the least possible value of
Answer: E
Small Hint:
A segment from to tangent to this circle makes the inradius or the semiperimeter of the right triangle with legs
Big Hint:
For the inradius case, so positive divisors of count the oriented segments
Solution:
The circle centered with radius is tangent to both axes. A segment from to with is tangent to it when equals either the inradius or the semiperimeter of the right triangle with legs
In the inradius case, put and Then and every positive divisor determines one oriented segment, with and Thus there are exactly such segments.
For these counts are and no semiperimeter case is possible because the smallest integer right triangle has semiperimeter At and the -- triangle contributes two more oriented segments. Hence is the least possible radius and gives exactly segments.
The two semiperimeter segments have In the inradius family, is largest at or giving Therefore and
Thus, the correct answer is E.
Problem 25 in Other Years
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