Use a piece of rectangular paper with a length of 2.5 cm and a width of 2 cm to cut a circle with a radius of 1 cm. What is the maximum utilization rate of this paper?
用一张长2.5厘米，宽2厘米的长方形纸剪半径1厘米的圆，最多能这张纸的利用率是多少．
<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">2.5 * 2</gadget>
<output>5</output>

<gadget id="calculator">3.14 / 5</gadget>
<output>0.628</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">0.628 * 1</gadget>
<output>0.628</output>

<result>0.628</result>