If the radius of the circle is shortened by 30%, how much is the area reduced?
把圆的半径缩短30%，则面积减少多少
<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

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

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 * (7/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(7/10) ** 2</gadget>
<output>49/100 = around 0.49</output>

<gadget id="calculator">3.14 * (49/100)</gadget>
<output>1.5386</output>

<gadget id="calculator">3.14 - 1.5386</gadget>
<output>1.6014</output>

<gadget id="calculator">1.6014 / 3.14</gadget>
<output>0.51</output>

<result>0.51</result>