Multiple choice general knowledge math & puzzles If the radius of a circle is diminished by 10%, then its area is diminished by: 10% 19% 20% 36% Reveal answer Fill a bubble to check yourself B Correct answer Explanation Area is proportional to the square of the radius. If the radius becomes 0.9r, the area becomes (0.9)^2 = 0.81 of the original area. The decrease is 1 - 0.81 = 0.19, or 19%.