The engineering team planned to build an 18.9-kilometer-long road in 21 days, but it took only 18 days to complete the construction. How many kilometers were built per day more than planned?
工程队计划用21天修一条长18.9千米的公路，结果只用了18天修完，结果比计划每天多修多少千米？
<gadget id="calculator">18.9 / 18</gadget>
<output>1.05</output>

<gadget id="calculator">18.9 / 21</gadget>
<output>0.9</output>

<gadget id="calculator">1.05 - 0.9</gadget>
<output>0.15</output>

<result>0.15</result>