The price of chocolate candy is 30 yuan per kilogram, and the price of toffee is 18 yuan per kilogram. How much lower is the price of toffee than chocolate candy?
巧克力糖每千克售价30元，奶糖每千克售价18元．奶糖的售价比巧克力糖低百分之几？
<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>