Master Wang processes a batch of parts at a rate of 120 per hour. When 60 more (4/5) of all tasks are processed, the work efficiency is reduced to only 75% of the original. It took 20 minutes more than the planned time to process all the parts in this way. How many parts are there in this batch?
王师傅加工一批零件，每小时加工120个，当加工了全部任务的(4/5)多60个时，工作效率降低，只有原来的75%．这样加工完成全部零件，比计划的时间多用了20分钟，这批零件一共有多少个？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">(4/3) - 1</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) / (1/3)</gadget>
<output>1</output>

<gadget id="calculator">120 * 1</gadget>
<output>120</output>

<gadget id="calculator">120 + 60</gadget>
<output>180</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">180 / (1/5)</gadget>
<output>900</output>

<result>900</result>