Master Li wants to process a batch of parts. He plans to make 30 parts a day, and he can complete the task 6 days in advance; when he actually processes 40 parts a day, he can complete the task 10 days in advance. How many parts are there in total?
李师傅要加工一批零件，计划每天做30个，可以提前6天完成任务；实际每天加工40个，则提前10天完成．求这批零件共有多少个？
<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/30) - (1/40)</gadget>
<output>1/120 = around 0.008333</output>

<gadget id="calculator">4 / (1/120)</gadget>
<output>480</output>

<result>480</result>