Master Zhang processes a batch of parts. (1/4) of this batch of parts is completed on the first day. If 15 more parts are processed on the second day, 50% of this batch of parts will be completed in two days. How many parts are there in this batch?
张师傅加工一批零件．第一天完成了这批零件的(1/4)，如果第二天再加工15个，两天就完成这批零件的50%．这批零件有多少个？
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) - (1/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">15 / (1/4)</gadget>
<output>60</output>

<result>60</result>