To make a wooden box with a length of 20 decimeters, a width of 15 decimeters, and a height of 10 decimeters without a cover, how many square meters of wooden boards are needed at least?
做一个长是20分米，宽是15分米，高是10分米的无盖木箱，至少需要多少平方米的木板？
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">20 * 10 * 2</gadget>
<output>400</output>

<gadget id="calculator">15 * 10 * 2</gadget>
<output>300</output>

<gadget id="calculator">300 + 400 + 300</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 / 100</gadget>
<output>10</output>

<result>10</result>