Xinguang Township built a 2.1-kilometer-long embankment. The first 5 days averaged 0.12 kilometers per day, and the rest took 5 days to complete. How many kilometers per day on average?
新光乡修一条长2.1千米的河堤，前5天平均每天修0.12千米，余下的要5天修完，平均每天修多少千米？
<gadget id="calculator">0.12 * 5</gadget>
<output>0.6</output>

<gadget id="calculator">2.1 - 0.6</gadget>
<output>1.5</output>

<gadget id="calculator">1.5 / 5</gadget>
<output>0.3</output>

<result>0.3</result>