A and B work together to process a batch of machine parts, and they process exactly 30% of this batch of parts in 9 days. At this time, A has processed 72 more parts than B. If A can process this batch of parts alone in 40 days, how many parts are there in this batch?
甲乙两人共同加工一批机器零件，9天正好加工了这批零件的30%，这时甲比乙多加工了72个零件．如果甲单独加工这批零件40天可以完成，这批零件有多少个？
<gadget id="calculator">72 / 9</gadget>
<output>8</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/10) / 9</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/30) - (1/40)</gadget>
<output>1/120 = around 0.008333</output>

<gadget id="calculator">8 / (1/120)</gadget>
<output>960</output>

<result>960</result>