To cut three circles with a diameter of 10 cm, at least one piece of rectangular paper with an area of square centimeters must be prepared.
要剪3个直径10厘米的圆，至少要准备一张面积是多少平方厘米的长方形纸．
<gadget id="calculator">10 * 2 * 3</gadget>
<output>60</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">60 * 20</gadget>
<output>1_200</output>

<result>1_200</result>