To build a canal, if the plan is to build 0.28 kilometers per day, it can be completed in 30 days. Actually repair 0.42 kilometers per day. How many days less than the original plan can actually complete the task?
修一条水渠，如果计划每天修0.28千米，30天可以完成．实际每天修0.42千米．实际比原计划可以少用多少天完成任务？
<gadget id="calculator">30 / 0.42</gadget>
<output>71.428571</output>

<gadget id="calculator">0.28 * 71.428571</gadget>
<output>20</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<result>10</result>