If a cone has a volume of 81 cubic meters and a height of 3 meters, what is the area of the base in square meters?
一个圆锥的体积为81立方米，高为3米，则底面积为多少平方米．
<gadget id="calculator">3 / 3</gadget>
<output>1</output>

<gadget id="calculator">81 * 1</gadget>
<output>81</output>

<result>81</result>