batch of parts was equally distributed to the master and the apprentice to make at the same time. As a result, the master finished it 2 hours earlier. It is known that the master processes 30 per hour and the apprentice processes 25 per hour. How many parts are in this batch?
一批零件，均分给师徒二人同时去做，结果师傅提早2小时完成，已知师傅每小时加工30个，徒弟每小时加工25个，这批零件多少个？
<gadget id="calculator">30 - 25</gadget>
<output>5</output>

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

<gadget id="calculator">25 * (2/5) * 30 * 2</gadget>
<output>600</output>

<result>600</result>