Do you have a map?

I want to ask the original question: it is known that the area of the shadow part in the picture below is 20 square centimeters, and the area of the circle is how many square centimeters?

First, it can be determined that the shadow part in the lower right corner is a big square-small square = shadow area.

The side length of a big square is actually equal to the radius of the outer circle (R), and the side length of a small square is equal to the radius of the inner circle (R).

Then the area of the big square: S=R×R the area of the small square =R×R.

The area of the shaded part is equal to R×R-r×r is equal to (the square of r-the square of r).

Note that the area of the lower ring is equal to π(R squared -r squared).

Through transformation, we can get that the area of the ring is equal to π× the area of the shadow part.

Calculation process: S big positive =R×R S small positive =R×R.

R×R-r×r equals 20.

S ring =π(R×R-r×r)

=3. 14×20

=62.8 square centimeters

A: The area of the ring is 62.8 square centimeters.

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