There is a batch of cement on the construction site, which was transported away for the first time (2/5), and transported away for the second time (7/20), leaving 180 tons. How many tons is this batch of cement?
工地上有一批水泥，第一次运走了(2/5)，第二次运走了(7/20)，还剩下180吨．这批水泥一共有多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">7 / 20</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">1 - (2/5) - (7/20)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">180 / (1/4)</gadget>
<output>720</output>

<result>720</result>