pile of coal is planned to burn 4 tons per day and can be burned for 72 days. Due to the improvement of the stove, 0.8 tons can be saved every day. In this way, how many days can this pile of coal be burned? (Solve with ratio)
一堆煤计划每天烧4吨可以烧72天．由于改进炉灶，每天节约0.8吨，这样，这堆煤可烧多少天？(用比例解)
<gadget id="calculator">4 * 72</gadget>
<output>288</output>

<gadget id="calculator">4 - 0.8</gadget>
<output>3.2</output>

<gadget id="calculator">288 / 3.2</gadget>
<output>90</output>

<result>90</result>