The cost of a machine part is 3 yuan, and the selling price is 3.45 yuan, so what is its profit margin?
一个机器零件的成本是3元，出售价是3.45元，那么它的利润率是多少．
<gadget id="calculator">3.45 - 3</gadget>
<output>0.45</output>

<gadget id="calculator">0.45 / 3</gadget>
<output>0.15</output>

<result>0.15</result>