A batch of parts, 120 per hour, takes 20 hours to complete. If it takes 15 hours to complete, how many parts need to be produced per hour? (Solve with ratio)
一批零件，每小时生产120个，需要20小时完成．如果要求15小时完成，每小时需要生产多少个零件？(用比例解)
<gadget id="calculator">120 * 20</gadget>
<output>2_400</output>

<gadget id="calculator">2_400 / 15</gadget>
<output>160</output>

<result>160</result>