A pile of coal was originally planned to burn 4 tons per day, and it can be burned for 72 days. Due to the improvement of the stove, it actually burns 3.2 tons per day. How many more days can this pile of coal be burned?
一堆煤原计划每天烧4吨，可烧72天，由于改进炉灶，实际每天烧3.2吨，这堆煤可多烧多少天？
<gadget id="calculator">72 / 3.2</gadget>
<output>22.5</output>

<gadget id="calculator">4 * 22.5</gadget>
<output>90</output>

<gadget id="calculator">90 - 72</gadget>
<output>18</output>

<result>18</result>