A batch of rice sold 20% in the first week and 200kg in the second week, leaving 440kg. How many kilograms does this batch of rice have?
一批大米，第一周卖出20%，第二周卖出200kg，还剩440kg，这批大米有多少kg？
<gadget id="calculator">200 + 440</gadget>
<output>640</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">640 / (4/5)</gadget>
<output>800</output>

<result>800</result>