To build a canal, the original plan was to build 0.24 kilometers per day, but the actual daily construction was 0.06 kilometers more than the original plan. After 12 days, there is still 0.4 kilometers left unrepaired. How many kilometers is this canal?
修一条水渠，原计划每天修0.24千米，实际每天比原计划多修0.06千米．12天后还差0.4千米没修．这条水渠长是多少千米？
<gadget id="calculator">0.24 + 0.06</gadget>
<output>0.3</output>

<gadget id="calculator">0.3 * 12</gadget>
<output>3.6</output>

<gadget id="calculator">3.6 + 0.4</gadget>
<output>4</output>

<result>4</result>