A batch of parts is processed, 200 are processed on the first day, and 250 are processed on the second day. (3/5) of these parts are processed in these two days. How many parts are there in this batch?
加工一批零件，第一天加工200个，第二天加工250个，这两天共加工了这批零件的(3/5)．这批零件共有多少个？
<gadget id="calculator">200 + 250</gadget>
<output>450</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">450 / (3/5)</gadget>
<output>750</output>

<result>750</result>