To make 10 cuboid iron chimneys, each section is 4 decimeters long, 3 decimeters wide, and 20 decimeters high, at least how many square meters of iron sheets are needed.
要制作10节长方体的铁皮烟囱，每节长4分米，宽3分米，高20分米，至少要用多少平方米的铁皮．
<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<gadget id="calculator">3 * 20</gadget>
<output>60</output>

<gadget id="calculator">80 + 60</gadget>
<output>140</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">140 * 2 * (1/10)</gadget>
<output>28</output>

<result>28</result>