A section of the road is 324 meters long, 240 meters have been repaired, and the rest is planned to be completed in 4 hours. How many meters are repaired per hour on average?
一段路长324米，已经修了240米，剩下的计划4小时修完．平均每小时修多少米？
<gadget id="calculator">324 - 240</gadget>
<output>84</output>

<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<result>21</result>