A cylindrical iron drum without a lid has a base radius of 20 cm and a height of 50 cm. How many square centimeters of iron sheet is needed to make such an iron drum? (π takes 3.14)
一个无盖的圆柱形铁桶，底面半径是20厘米，高是50厘米，制作这样一个铁桶至少需要多少平方厘米的铁皮？(π取3.14)
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">3.14 * 400</gadget>
<output>1_256</output>

<gadget id="calculator">3.14 * 20 * 2 * 50</gadget>
<output>6_280</output>

<gadget id="calculator">1_256 + 6_280</gadget>
<output>7_536</output>

<result>7_536</result>