A pile of coal was originally planned to burn 4 tons per day, and it can be burned for 72 days. Since the improved technology saves 0.4 tons per day, how many days can this pile of coal be burned? (Solve with ratio)
一堆煤原计划每天烧4吨，可以烧72天，由于改进技术每天节约0.4吨，这堆煤可以烧多少天？(用比例解)
<gadget id="calculator">72 * 4</gadget>
<output>288</output>

<gadget id="calculator">4 - 0.4</gadget>
<output>3.6</output>

<gadget id="calculator">288 / 3.6</gadget>
<output>80</output>

<result>80</result>