After a pile of coal is used up (1/6), there are still 150 tons left. How many tons is 20% of this pile of coal?
一堆煤用去(1/6)后，还剩150吨，这堆煤的20%是多少吨．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">150 / (5/6)</gadget>
<output>180</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">180 * (1/5)</gadget>
<output>36</output>

<result>36</result>