There are 8 doors of the same size in the classroom of 4 classes of the third grade, each door is 2m high and 9dm wide. What is the minimum square decimeter of planks needed to make these doors?
三年级4个班的教室共有8扇相同大小的门，每扇门高2m，宽9dm．做这些门至少需要多少平方分米的木板？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">20 * 9 * 8</gadget>
<output>1_440</output>

<result>1_440</result>