The school cafeteria bought some salt, and planned to use 2.4kg per day, which would be used up in 30 days. Actually use less than 0.4kg per day, how many days will it be used up?
学校食堂购进一些食盐，计划每天用2.4㎏，30天用完．实际每天少用0.4㎏，实际多少天用完？
<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>