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 = \(pi * r^2\)

=\(pi *10^2\)

=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 = \(pi * 8^2\)

=64pi

Therefore the area of the circular region decreased = \(\frac{(New - old)}{old}\) = \(\frac{(64pi - 100pi)}{100pi}\)= \(-36%\) (The value is negative because the percentage is decreased)

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