The area of a circle is 5 square centimeters, and its radius is enlarged by 2:1, what is the area of the enlarged circle in square centimeters?
一个圆的面积是5平方厘米，把它的半径按2：1放大，放大后的圆的面积是多少平方厘米．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>