If the circumference of a circle is reduced by 30%, how much is the area reduced?
一个圆周长减少30%，面积减少多少
<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">(7/10) * (7/10)</gadget>
<output>49/100 = around 0.49</output>

<gadget id="calculator">1 - (49/100)</gadget>
<output>51/100 = around 0.51</output>

<result>51/100 = around 0.51</result>