The water in a water tank is full (4/5), and after 25% is used, the remaining water is 210 liters more than used. How many liters of water is this tank filled with?
一个水箱中的水是装满时的(4/5)，用去25%后，剩余的水比用去的多210升．这个水箱装满水是多少升．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4) - (1/4)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">210 / (1/2)</gadget>
<output>420</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">420 / (4/5)</gadget>
<output>525</output>

<result>525</result>