cylindrical bucket has a base diameter of 30 cm and a height of 40 cm. Add an iron hoop to this bucket to fix it, how much material is needed at least?
一个圆柱形水桶的底面直径是30厘米，高是40厘米．给这个水桶加一圈铁箍用于固定，至少需要多少材料？
<gadget id="calculator">3.14 * 30</gadget>
<output>94.2</output>

<result>94.2</result>