There are two circles, big and small. The sum of their areas is 78 square centimeters. The radius of the small circle is 20% of the radius of the big circle. What is the area of the big circle in square centimeters?
有大小两个圆，它们的面积之和为78平方厘米，小圆的半径是大圆半径的20%，大圆的面积是多少平方厘米．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / (1/5)</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">25 / 1</gadget>
<output>25</output>

<gadget id="calculator">25 + 1</gadget>
<output>26</output>

<gadget id="calculator">78 / 26</gadget>
<output>3</output>

<gadget id="calculator">3 * 25</gadget>
<output>75</output>

<result>75</result>