Master Zhang processes a batch of parts. The ratio of the number completed on the first day to the total number is 2:5. If 25 more parts are processed, half of this batch of parts will be completed. How many parts are there in total?
张师傅加工一批零件，第一天完成的个数与总个数的比为2：5，如果再加工25个，就完成了这批零件的一半，这批零件共有多少个？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">25 / (1/10)</gadget>
<output>250</output>

<result>250</result>