The diagram shows circular sections of a cone. If x is 20 percent of R

The cone does not matter; all we need are areas of two circles.

Choose values

Let R = 5
Let x = 1 (20 percent of 5)

Area of Circle C = \(25\pi\)
Area of Circle B = \(1\pi\)

By what percentage is the area of circle C greater than the area of circle B?

Percent increase = \(\frac{(New - Old)}{Old} * 100\)

\(\frac{(25\pi - 1\pi)}{1\pi} * 100\)

\(\frac{24}{1} * 100\) = 2400 percent

Circle C's area is 2400 percent greater than Circle B's area

ANSWER D

Use multiplier / scale factor
x = .20R

Area of Circle C = \(\pi*R^2\)

Let area of C, \(\pi*R^2 = X\)

Area of Circle B =
(scale factor)\(^2\) * (Area of C)

\((.2)^2(X) =.04X =\)Area of B

Percent increase =

\(\frac{(X) - (.04X)}{(.04X)} * 100\)

\(\frac{.96X}{.04X} = (24 * 100)\) = 2400 percent

Answer D

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