The master and apprentice have to process 720 parts, and 240 were processed in the first 4 hours. According to this calculation, how many hours will it take to process the remaining parts? (Answer with proportional knowledge)
师徒两人要加工720个零件，前4小时加工了240个，照这样计算，剩下的零件还要几小时才能加工完？(用比例知识解答)
<gadget id="calculator">720 - 240</gadget>
<output>480</output>

<gadget id="calculator">4 * 480</gadget>
<output>1_920</output>

<gadget id="calculator">1_920 / 240</gadget>
<output>8</output>

<result>8</result>