A kind of fountain pen, the original price is 18.6 yuan per box, the current price is 15.81 yuan per box, ask: How much is the current price lower than the original price?
一种水笔，原价每盒18.6元，现价每盒15.81元，求：现价比原价降低了百分之几？
<gadget id="calculator">18.6 - 15.81</gadget>
<output>2.79</output>

<gadget id="calculator">2.79 / 18.6</gadget>
<output>0.15</output>

<result>0.15</result>