A cylindrical iron bucket without a cover is 50 cm high and 40 cm in diameter at the bottom. How much iron is needed to make this bucket?
一个无盖的圆柱形铁皮水桶，高50厘米，底面直径40厘米，做这个水桶大约需用多少铁皮？
<gadget id="calculator">3.14 * 40 * 50</gadget>
<output>6_280</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

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

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

<result>7_536</result>