Make a cube tank with side length 3m. How much m**2 is the minimum iron sheet needed to make this water tank?
做一个正方体水箱，棱长是3m．做这个水箱至少需要铁皮多少m**2？
<gadget id="calculator">3 * 3 * 6</gadget>
<output>54</output>

<result>54</result>