The electric motor factory wants to produce a batch of generators. It originally planned to produce 20 generators per day, and it took 12 days to complete. In fact, it actually produced 10 more generators per day. How many days did it actually take? (Solve with ratio)
电机厂要生产一批发电机，原计划每天生产20台，12天完成，实际每天多生产10台，实际用多少天完成？(用比例解)
<gadget id="calculator">20 * 12</gadget>
<output>240</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">240 / 30</gadget>
<output>8</output>

<result>8</result>