To make a metal water tank with a length of 40 cm, a width of 30 cm, and a height of 25 cm, at least how many square centimeters of iron sheet are needed.
做一个长40厘米、宽30厘米、高25厘米的无盖铁皮水箱，至少需要铁皮多少平方厘米．
<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">40 * 25 * 2</gadget>
<output>2_000</output>

<gadget id="calculator">30 * 25 * 2</gadget>
<output>1_500</output>

<gadget id="calculator">1_200 + 2_000 + 1_500</gadget>
<output>4_700</output>

<result>4_700</result>