1952 AMC 12 Problem 1

Attempt Problem 1 of the 1952 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 1952 AMC 12 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

1.

If the radius of a circle is a rational number, its area is given by a number which is:
Rational
Irrational
Integral
A perfect square
None of these
Answer: B
Concepts:circlecircle area
Small hint:
Write the area in terms of the radius and π\pi
Big hint:
A circle’s radius is positive, so its rational square is nonzero
Solution:
If the positive rational radius is r,r, then its area is πr2.\pi r^2. The factor r2r^2 is a nonzero rational number, and a nonzero rational multiple of the irrational number π\pi is irrational.
Thus, the correct answer is B.
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