7 tons of cement, 20% of it is transported away each time, how many times it is transported.
7吨水泥，每次运走它的20%，多少次运完．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">7 * (1/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">7 / (7/5)</gadget>
<output>5</output>

<result>5</result>