batch of parts, the master alone needs 18 hours to complete, and the apprentice can make 30 per hour. Now the master and the apprentice are working together. When the task is completed, the apprentice has made 40% of all the parts. How many parts are there in total?
一批零件，师傅单独做需要18小时完成，徒弟每小时可以做30个，现在师徒二人合做，完成任务时，徒弟做了全部零件的40%，这批零件共多少个？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / (2/5)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">30 * (3/2) * 18</gadget>
<output>810</output>

<result>810</result>