Master Zhang processes a batch of parts. The ratio of the number of processed parts to the total number on the first day is 1:4. If another 60 parts are processed, the ratio of the number of processed parts to the number of unprocessed parts is 1:2. How many parts are there?
张师傅加工一批零件，第一天加工的个数与总个数的比1：4，如果再加工60个，那么已加工的个数与未加工的个数比是1：2，这批零件有多少个？
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">(1/3) - (1/4)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">60 / (1/12)</gadget>
<output>720</output>

<result>720</result>