A batch of parts is processed, (1/4) of this batch of parts is processed on the first day, 210 are processed on the second day, (2/5) of this batch of parts is processed in two days, how many parts are there in this batch?
加工一批零件，第一天加工了这批零件的(1/4)，第二天加工210个，两天共加工了这批零件的(2/5)，这批零件共有多少个？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(2/5) - (1/4)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">210 / (3/20)</gadget>
<output>1_400</output>

<result>1_400</result>