Add part of the water into the cylindrical iron bucket, put a cylindrical steel block with a bottom radius of 5cm into the water (stand vertically), and the water level in the bucket will rise by 7cm; if the round steel is exposed to the water surface by 15cm, the water surface in the bucket will If the drop is 3cm, what is the surface area of the round steel in cm**2 (the result remains π)
将圆柱体铁桶中加入部分水，把一个底面半径为5cm的圆柱体钢块完全放入水中(竖直放立)，桶里水面上升7cm；如果再将圆钢露出水面15cm，桶里水面则下降3cm，则圆钢的表面积是多少cm**2(结果保留π)
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">25 * 15</gadget>
<output>375</output>

<result>375</result>