There is a pile of cement, (4/5) is removed, and (4/5) tons are left, how many tons are there in this pile of cement?
有一堆水泥，运走(4/5)，还剩(4/5)吨，这堆水泥共有多少吨．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

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

<result>4</result>