A kind of mineral water, the retail price is 2.2 yuan per bottle. In order to thank the customers for their love for the product, the manufacturer specially launched a "buy three get one free" big bargain activity. The manufacturer's practice is much more favorable.
一种矿泉水，零售每瓶卖2.2元，生产厂家为感谢广大顾客对产品的厚爱，特开展"买三赠一"大酬宾活动，生产厂家的做法优惠了多少．
<gadget id="calculator">4 * 2.2</gadget>
<output>8.8</output>

<gadget id="calculator">3 * 2.2</gadget>
<output>6.6</output>

<gadget id="calculator">8.8 - 6.6</gadget>
<output>2.2</output>

<gadget id="calculator">2.2 / 8.8</gadget>
<output>0.25</output>

<result>0.25</result>