A cubic water tank without a cover has a side length of 7dm. How many square decimeters of iron sheets are used to make this water tank?
一个无盖的正方体水箱，棱长7dm，制作这个水箱至少用了多少平方分米的铁皮？
<gadget id="calculator">7 * 7 * 5</gadget>
<output>245</output>

<result>245</result>