To dig a canal, dig 11.8km on the first day, which is 0.12km less than that on the second day, and there is 0.4km left to be dug. How long is this canal in kilometers?
挖一条水渠，第一天挖11.8km，比第二天少挖0.12km，还剩0.4km没有挖．这条水渠全长多少千米？
<gadget id="calculator">11.8 + 0.12</gadget>
<output>11.92</output>

<gadget id="calculator">11.8 + 11.92 + 0.4</gadget>
<output>24.12</output>

<result>24.12</result>