If a cylinder has a diameter and height of 6 cm and is cut into two half cylinders along the diameter, how many square centimeters will the surface area increase?
一个圆柱体的直径和高都是6厘米，沿着直径切成两个半圆柱，表面积增加了多少平方厘米．
<gadget id="calculator">6 * 6 * 2</gadget>
<output>72</output>

<result>72</result>