After using (1/4) of a batch of rice, another 306 kilograms were added. At this time, this batch of rice is more (1/5) than the original one. How many kilograms does this batch of rice weigh?
一批大米，用了(1/4)后又进了306公斤，这时这批大米比原来多(1/5)，问原来这批大米有多少公斤？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(1/5) - (3/4)</gadget>
<output>-11/20 = around -0.55</output>

<gadget id="calculator">1 + (-11/20)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">306 / (9/20)</gadget>
<output>680</output>

<result>680</result>