To take the air-conditioned bus, each person needs to insert a coin of 2 yuan. If you use an IC card, you will be deducted 1.6 yuan each time. How much cheaper is it to pay by card than by coin?
乘坐空调公交车每人需投币2元，如果刷IC卡，则每次扣费1.6元．刷卡比投币便宜了百分之几？
<gadget id="calculator">2 - 1.6</gadget>
<output>0.4</output>

<gadget id="calculator">0.4 / 2</gadget>
<output>0.2</output>

<result>0.2</result>