If the radius of a circle is reduced by 40%, how much will its area be reduced?
一个圆的半径比原来减少40%，那么它的面积比原来减少多少．
<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

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

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

<gadget id="calculator">(3/5) ** 2</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">3.14 * (9/25)</gadget>
<output>1.1304</output>

<gadget id="calculator">3.14 - 1.1304</gadget>
<output>2.0096</output>

<gadget id="calculator">2.0096 / 3.14</gadget>
<output>0.64</output>

<result>0.64</result>