sandy wrote:
If the radius of a circular region were decreased by 20 percent, the area of the circular region would decrease by what percent?
A. 16%
B. 20%
C. 36%
D. 40%
E. 44%
Let us take the radius as = 10
Therefore the area of the circular region =
pi∗r2=
pi∗102=100pi
Now the radius is decreased by 20 percent
i.e 10-(10 * 0.2) = 8, which is the new radius
Therefore area of the circular region with the new radius =
pi∗82=64pi
Therefore the area of the circular region decreased =
(New−old)old =
(64pi−100pi)100pi=
−36 (The value is negative because the percentage is decreased)