After selling 25% of a batch of rice, another 500 kg is shipped in. At this time, the rice is the original (4/5), how many kg is the original?
一批大米，卖出它的25%后，又运进500千克，这时的大米是原来的(4/5)，原有多少千克？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">25 / 100</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">(4/5) - (3/4)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">500 / (1/20)</gadget>
<output>10_000</output>

<result>10_000</result>