There is a circular iron sheet with a radius of 20 centimeters, 40% is used for decoration, how many square centimeters are left?
有一块圆形铁皮，半径为20厘米，搞装潢用去40%，还剩下多少平方厘米？
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">3.14 * 400 * (3/5)</gadget>
<output>753.6</output>

<result>753.6</result>