How many square meters of iron sheet should be used to make 10 cylindrical ventilation pipes with a length of 5 meters and a radius of 0.5 meters?
做10节长5米，半径0.5米的圆柱形通风管，至少要用多少平方米的铁皮？
<gadget id="calculator">3.14 * 0.5 * 2 * 5 * 10</gadget>
<output>157</output>

<result>157</result>