Fill two cylindrical containers with an inner diameter of 20 cm and 30 cm and a height of 40 cm with water, and then pour the water in the two containers into a cylindrical container with an inner diameter of 50 cm and a height of 60 cm What is the height of the water surface in centimeters.
将内口直径分别为20和30厘米，高都为40厘米的两个圆柱形容器注满水，再将两容器的水都倒入内口直径为50厘米、高为60厘米的圆柱形容器中，水面高度为多少厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 40</gadget>
<output>12_560</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 ** 2</gadget>
<output>225</output>

<gadget id="calculator">3.14 * 225 * 40</gadget>
<output>28_260</output>

<gadget id="calculator">12_560 + 28_260</gadget>
<output>40_820</output>

<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">25 ** 2</gadget>
<output>625</output>

<gadget id="calculator">3.14 * 625</gadget>
<output>1_962.5</output>

<gadget id="calculator">40_820 / 1_962.5</gadget>
<output>20.8</output>

<result>20.8</result>