To make two ventilation pipes 2 meters long, the diameter of the ventilation opening is 1 decimeter, and [the welding part is 1 centimeter] requires white iron sheet [how much]
做2米长的两根通风管，通风口直径为1分米，〔焊接处为1厘米〕需要白铁皮〔多少〕
<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">3.14 + 1</gadget>
<output>4.14</output>

<gadget id="calculator">4.14 * 2 * 2</gadget>
<output>16.56</output>

<result>16.56</result>