In a rectangle with a length of 30 cm and a width of 18 cm, draw the largest circle, what is the radius of this circle in cm? ．
在一个长30厘米，宽18厘米的长方形中，画一个最大的圆，这个圆的半径是多少厘米．．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>