A batch of coal shipped from a factory plans to burn 2.4 tons per day, and it will be burnt out in 30 days. Due to improved technology, it will burn 0.4 tons less per day. How many days can this batch of coal actually be burned? (Solve with ratio)
某工厂运来一批煤，每天计划烧2.4吨，30天烧完，由于改进技术，每天少烧0.4吨，这批煤实际可烧多少天？(用比例解)
<gadget id="calculator">2.4 * 30</gadget>
<output>72</output>

<gadget id="calculator">2.4 - 0.4</gadget>
<output>2</output>

<gadget id="calculator">72 / 2</gadget>
<output>36</output>

<result>36</result>