Make the largest circle with wire. If the wire is shortened by 20%, how much will the area of the circle be reduced?
用铁丝围一个最大的圆．若将铁丝缩短20%，则围成的圆的面积将减少多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * (4/5)</gadget>
<output>16/25 = around 0.64</output>

<gadget id="calculator">1 - (16/25)</gadget>
<output>9/25 = around 0.36</output>

<result>9/25 = around 0.36</result>