There is a circular fish pond in Hongyan Village. In the middle of the fish pond is a small circular island planted with trees. The radius of the fish pond is 15 meters, and the radius of the island is 4 meters. How many square meters is the water area of the fish pond?
红岩村有一个圆形鱼塘，鱼塘中间有一个圆形小岛，种着树木，鱼塘的半径是15米，小岛的半径是4米．鱼塘的水域面积是多少平方米？
<gadget id="calculator">15 ** 2</gadget>
<output>225</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">225 - 16</gadget>
<output>209</output>

<gadget id="calculator">3.14 * 209</gadget>
<output>656.26</output>

<result>656.26</result>