Chen Dong's father's mobile phone prepaid card has a certain amount of money. If he spends 6 yuan a day, he can use it for 15 days. If spending 4.5 yuan per day, how many days can this stored-value card be used for? (Solve with ratio)
陈东爸爸的手机储值卡有一定数额的钱，如果每天消费6元，能使用15天．如果每天消费4.5元，这张储值卡可以使用多少天？(用比例解)
<gadget id="calculator">6 / 4.5</gadget>
<output>1.333333</output>

<gadget id="calculator">15 * 1.333333</gadget>
<output>19.999995</output>

<result>19.999995</result>