Master Zhang processes a batch of parts. The ratio of the number of completed parts to the total number of parts on the first day is 1:3. If he processes 25 more parts, half of this batch of parts will be completed. How many parts are there in this batch?
张师傅加工一批零件，第一天完成的个数与零件的总个数的比是1﹕3，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">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">25 / (1/6)</gadget>
<output>150</output>

<result>150</result>