When processing a batch of parts, the ratio of completed parts to unfinished parts is 1:2. If 30 more parts are processed, then half of the work is completed. How many parts are there in this batch?
加工一批零件，已完成个数与未完成个数的比是1：2，如果再加工30个，那么就完成了一半，这批零件一共有多少个？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">30 / (1/6)</gadget>
<output>180</output>

<result>180</result>