For a pile of coal, 20 tons have been used, and the rest is 25% of the used amount. How many tons is this pile of coal in total?
一堆煤，用去了20吨，余下的是用去的25%，这一堆煤一共多少吨？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 * (1/4)</gadget>
<output>5</output>

<gadget id="calculator">20 + 5</gadget>
<output>25</output>

<result>25</result>