A certain unit of the People’s Liberation Army is conducting military training. It has to march 502 kilometers, and it has already traveled 460 kilometers. The remaining distance is completed in 2 days. How many kilometers per day?
解放军某部进行军事训练，要行军502千米，已经走了460千米，余下的路程2天走完，每天走多少千米？
<gadget id="calculator">502 - 460</gadget>
<output>42</output>

<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<result>21</result>