A cylinder has a base radius of 7 cm and a surface area of 1406.72 cm2. What is the height of this cylinder?
一个圆柱体，底面半径是7厘米，表面积是1406.72平方厘米．这个圆柱的高是多少？
<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">3.14 * 49 * 2</gadget>
<output>307.72</output>

<gadget id="calculator">1_406.72 - 307.72</gadget>
<output>1_099</output>

<gadget id="calculator">2 * 3.14 * 7</gadget>
<output>43.96</output>

<gadget id="calculator">1_099 / 43.96</gadget>
<output>25</output>

<result>25</result>