Iron hoops are placed on the periphery of a cylindrical wooden barrel. The diameter of the barrel is 60cm. How many decimeters of iron bars are needed to make three iron hoops like this? (neglected at joints)
一个圆柱形木桶外围打上铁箍，桶的直径是60cm，打这样的三条铁箍至少需要多少分米的铁条？(接头处忽略不计)
<gadget id="calculator">60 / 10</gadget>
<output>6</output>

<gadget id="calculator">3.14 * 6 * 3</gadget>
<output>56.52</output>

<result>56.52</result>