A cuboid ventilation pipe is 10 decimeters, and its width and height are both 4 decimeters. To make 100 such ventilation pipes, how many square meters of iron sheets are needed.
长方体通风管10分米，宽和高都是4分米，要制作100个这样的通风管，需要多少平方米的铁皮．
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">40 + 40</gadget>
<output>80</output>

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

<gadget id="calculator">80 * 2 * 1</gadget>
<output>160</output>

<result>160</result>