There is a pile of coal, 15 tons per day, which can be used for 40 days. If 40 tons are used in 10 days, according to this calculation, how many days will it take to use up this pile of coal? (answer with ratio)
有一堆煤，每天用15吨，可用40天．如果10天用40吨，照这样计算，用完这堆煤要用多少天？(用比例解答)
<gadget id="calculator">15 * 40</gadget>
<output>600</output>

<gadget id="calculator">40 / 10</gadget>
<output>4</output>

<gadget id="calculator">600 / 4</gadget>
<output>150</output>

<result>150</result>