Master Wang processes a batch of parts. Originally planned to process 30 parts per hour, it can be completed in 6 hours, but actually processes 40 parts per hour. How many hours does it actually take to process this batch of parts?
王师傅加工一批零件，原计划每小时加工30个，6小时可以完成，实际每小时加工40个，实际加工这批零件需要几小时？
<gadget id="calculator">6 / 40</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">30 * (3/20)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>