To process a batch of parts, A alone can complete it in 6 days, and B alone can complete it in 9 days. After the two work together for 3 days, there are still 260 parts left unfinished. How many parts are there in this batch?
加工一批零件，甲单独做6天完成，乙单独做9天完成，两人合做3天后，还剩下260个零件没有做．这批零件有多少个？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/6) + (1/9)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">(5/18) * 3</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 - (5/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">260 / (1/6)</gadget>
<output>1_560</output>

<result>1_560</result>