To build a canal, the original plan was to build 4.5 kilometers per day, and it took 20 days to complete. The actual repair was completed in 15 days. How much more kilometers was repaired per day than the original plan? (Solve with ratio)
修一条水渠，原计划每天修4.5千米，20天完成．实际15天修完，每天比原计划多修多少千米？(用比例解)
<gadget id="calculator">4.5 * 20</gadget>
<output>90</output>

<gadget id="calculator">4.5 * 15</gadget>
<output>67.5</output>

<gadget id="calculator">90 - 67.5</gadget>
<output>22.5</output>

<gadget id="calculator">22.5 / 15</gadget>
<output>1.5</output>

<result>1.5</result>