To make a cuboid bucket without a cover, the bottom surface is a square with a side length of 3 decimeters, and the height is 4 decimeters. How many square decimeters of iron sheet is needed at least?
做一个不带盖的长方体水桶，底面是边长为3分米的正方形，高是4分米，问至少需要多少平方分米的铁皮？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3 * 4 * 4</gadget>
<output>48</output>

<gadget id="calculator">9 + 48</gadget>
<output>57</output>

<result>57</result>