The store shipped 800 plastic boxes, bought in the morning (1/4), and sold in the afternoon (2/5). How many were sold in one day?
商店运来800只塑料盒，上午买出(1/4)，下午卖出(2/5)．一天共卖出多少只？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/4) + (2/5)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">800 * (13/20)</gadget>
<output>520</output>

<result>520</result>