cup of Coke is priced at 1.8 yuan. In order to promote sales, customers get a coupon for every cup of Coke bought. Every three coupons can be exchanged for a cup of Coke. How much is each coupon equivalent to?
一杯可乐售价1.8元，商家为了促销，顾客每买一杯可乐获一张奖券，每三张奖券可兑换一杯可乐，则每张奖券相当于多少元．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">1.8 / 4</gadget>
<output>0.45</output>

<result>0.45</result>