A section of iron sheet cylindrical downpipe is 2 meters long, the radius of the bottom surface is 2.5 decimeters, and the joint is 2 centimeters. How many square decimeters of iron sheet are needed to make this section of downwater pipe?
一节铁皮圆柱形下水管长2米，底面半径2.5分米，接头处2厘米，制作这节下水管至少需用铁皮多少平方分米．
<gadget id="calculator">3.14 * 2.5 * 2</gadget>
<output>15.7</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15.7 + (1/5)</gadget>
<output>15.9</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">15.9 * 20</gadget>
<output>318</output>

<result>318</result>