A, B, C, and D work together to process parts, A processes (1/2) of the other three, B processes (1/3) of the other three, C processes (1/5) of the remaining three, and D processes 30, how many parts are there in this batch?
甲乙丙丁四人合作加工零件，甲加工了其余三人的(1/2)，乙加工了其余三人的(1/3)，丙加工了其余三人的(1/5)，丁加工了30个，这批零件共有多少个？
<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 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/3) - (1/4) - (1/6)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / (1/4)</gadget>
<output>120</output>

<result>120</result>