The area of a circle is 15 square centimeters. If its radius is doubled, what is the area of the circle in square centimeters?
一个圆的面积是15平方厘米，将它的半径扩大2倍后，圆的面积是多少平方厘米．
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<result>60</result>