2007 AMC 8 Problem 16

Attempt Problem 16 of the 2007 AMC 8 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 2007 AMC 8 solutions, or check the answer key.

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

16.

Amanda Reckonwith draws five circles with radii 1,1, 2,2, 3,3, 44 and 5.5. Then for each circle she plots the point (C,A),(C, A), where CC is its circumference and AA is its area. Which of the following could be her graph?
Answer: A
Concepts:circle areacircumferencequadratic
Small hint:
Write circumference and area in terms of the radius.
Big hint:
As the circumference grows linearly with radius, the area grows quadratically.
Solution:
The circumferences of circles with radii 11 through 55 are 2π,2\pi, 4π,4\pi, 6π,6\pi, 8π,8\pi, and 10π10\pi. Their respective areas are π,\pi, 4π,4\pi, 9π,9\pi, 16π,16\pi, and 25π25\pi.
As CC increases by equal amounts, AA increases more and more quickly, so the points form an increasing quadratic pattern. Only graph A has that shape.
Thus, A is the correct answer.
LIVE by Po-Shen Loh
Programs

LIVE Classes

Self-Paced Classes

Stars

Scholarship

About Us

Who Is Po-Shen Loh?

Email Contact

Newsletter

Jobs

Become a Star

For a more Thought Full world.

© 2026 Expii, Inc.