It takes 20 days for A to complete a batch of parts. The two worked together for 10 days to complete this batch of parts (9/10). At this time, B made 480 parts. How many parts are there in total?
一批零件，甲独作要20天完成．二人合作10天完成这批零件的(9/10)，这时乙做了480个零件，这批零件共多少个？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(9/10) / 10</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(9/100) - (1/20)</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(1/25) * 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">480 / (2/5)</gadget>
<output>1_200</output>

<result>1_200</result>