The area of the base of a cylinder remains the same. If the height increases by 2 cm, the surface area increases by 62.8 cm**2. What is the area of the base of the cylinder in cm**2?
一个圆柱它的底面积不变，如果高增加2cm，表面积就增加62.8cm**2，这个圆柱的底面积是多少cm**2．
<gadget id="calculator">62.8 / 2</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

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

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>