It is known that the radius of circle A is equal to the diameter of circle B, and the sum of their areas is 100 square centimeters, so what is the area of circle A?
已知甲圆的半径长等于乙圆的直径长，且它们的面积之和是100平方厘米，那么甲圆的面积是多少？
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>