There is a cylinder, if its height increases by 1 cm, its lateral area will increase by 31.4 square centimeters. If its height is 20 cm, what is its volume in cubic centimeters?
有一个圆柱，如果高增加1厘米，它的侧面积就增加31.4平方厘米，如果它的高是20厘米，那么它的体积是多少立方厘米．
<gadget id="calculator">31.4 / 1 / 3.14 / 2</gadget>
<output>5</output>

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

<gadget id="calculator">3.14 * 25 * 10</gadget>
<output>785</output>

<result>785</result>