shadow area

=3×3- 1/4×3? ×3. 14+ 1/2×3×3

=9-7.065+4.5

=6.435

2. According to the stem analysis, we can get: r? -r？ = 15 cm2，

So the area of the ring =π(R? -r？ ),

=3. 14× 15,

=47. 1 (square centimeter),

A: The area of the ring is 47. 1 cm2.

So the answer is: 47. 1