Master Liu processed a batch of parts. On the first day, he processed 25% of this batch of parts. On the second day, he processed 100 parts. In two days, he processed a total of 45% of this batch of parts. How many parts are there in total?
刘师傅加工一批零件，第一天加工了这批零件的25%，第二天加工了100个，两天一共加工了这批零件的45%．这批零件一共有多少个？
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(9/20) - (1/4)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 / (1/5)</gadget>
<output>500</output>

<result>500</result>