If the radius of a circle is a centimeter, and 2:a=a:3, what is the area of the circle π square centimeters.
如果一个圆的半径是a厘米，且2：a=a：3，问这个圆的面积是多少π平方厘米．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<result>6</result>