To produce a batch of parts, A can make 18 parts per hour, and B can complete it in 12 hours alone. Now A and B are working together. When the task is completed, the ratio of the number of parts produced by A and B is 3:5. How many parts does A produce in total?
生产一批零件，甲每小时可做18个，乙单独做要12小时完成．现在由甲乙二人合做，完成任务时，甲乙生产零件的数量之比是3：5，甲一共生产零件多少个？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/12) * (3/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) + (1/20)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1 / (2/15)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">18 * (15/2)</gadget>
<output>135</output>

<result>135</result>