Xiaohong's father usually spends an average of 4.5 yuan in phone bills per day. He checked the phone bill balance in the mobile phone card and found that it can be used for 16 days. If you save 0.9 yuan every day from now on, how many days can you use these calls?
小红的爸爸通常平均每天消费4.5元话费，他查了一下手机卡中的话费余额，可以用16天．如果从现在起每天节约0.9元，这些话费可以用多少天？
<gadget id="calculator">4.5 - 0.9</gadget>
<output>3.6</output>

<gadget id="calculator">16 / 3.6</gadget>
<output>4.444444</output>

<gadget id="calculator">4.5 * 4.444444</gadget>
<output>19.999998</output>

<result>19.999998</result>