Master Zhang processes a batch of parts. The ratio of the number of completed parts to the total number on the first day is 1:3. If he processes 15 more parts, he can complete half of this batch of parts. The 15 parts processed again are the total number of parts ((( ))/(())).
张师傅加工一批零件，第一天完成的个数与总数的比是1：3，再加工15个，就可以完成这批零件的一半，再加工的15个零件是零件总数的((())/(()))．
<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>

<result>1/6 = around 0.166667</result>