How many square meters of iron sheet is required to make a cylindrical bucket with a base radius of 20cm and a height of 50cm?
用铁皮做一个底面半径是20cm，高是50cm的圆柱形无盖水桶，至少需要多少平方米的铁皮？
<gadget id="calculator">0.2 ** 2</gadget>
<output>0.04</output>

<gadget id="calculator">3.14 * 0.04</gadget>
<output>0.1256</output>

<gadget id="calculator">3.14 * 0.2 * 2 * 0.5</gadget>
<output>0.628</output>

<gadget id="calculator">0.1256 + 0.628</gadget>
<output>0.7536</output>

<result>0.7536</result>