If the radius of the circle is increased from 3 cm to 7 cm, the area of the circle increases by how many square centimeters.
圆的半径由3厘米增加至7厘米，圆的面积增加多少平方厘米．
<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">3.14 * 49</gadget>
<output>153.86</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">153.86 - 28.26</gadget>
<output>125.6</output>

<result>125.6</result>